Israel’s relationship with the Gulf states has been characterised as hostile since the former’s establishment as a state. Yet the shifting regional dynamics following the 2011 Arab Spring have dramatically affected these relations. In particular, relations between Israel and the Kingdom of Saudi Arabia (KSA)—an Arab state which sees itself as the leader of the Muslim world—have evidently improved after undergoing years of clandestine dealings.
Saudi-Israeli Relations: Past to Present
Following Israel’s establishment in 1948, the KSA refused to recognise Israel and endorsed the Arab world’s opposition to it.[i] By the 1980s, the KSA’s stance shifted to a role of mediation and initiation of peace proposals.[ii] Most notably, in 1981, Riyadh’s Fahd Plan proposed a complete Israeli departure from the lands it acquired in 1967, including East Jerusalem, and offered Palestinian refugees the choice of either returning to their homes or obtaining compensation, stating “all states in the region have the right to live in peace.”[iii] However, after “Arab hard-liners” rejected the plan for its implicit recognition of Israel,[iv] it was modified a year later (repackaged as the Fez Plan) and a statement calling for the region’s states to peacefully coexist was removed.[v] Nonetheless, the plan was not implemented. Among those that opposed the plan were Israeli policymakers who felt that the plan posed “a threat to Israel’s existence” and sought to “bring about Israel’s destruction in stages”[vi] because it failed to define the boundaries of a Palestinian state, affirmed the “right” of Palestinian refugees to return to Israel—thus presenting an existential threat to both Israel’s sovereignty and security—and recognized the Palestine Liberation Organization (designated by the US as a terrorist organization in 1987) as the sole legitimate representative of the Palestinian people.
Consequently, the KSA proposed the Abdullah Plan in 2002, which later became the Arab Peace Initiative (API). The API presented a plan which sought to attain Israel’s withdrawal from all lands it acquired in the 1967 Six Day war, the formation of an autonomous Palestinian state with East Jerusalem as its capital, and the establishment of “normal relations” between Israel and Arab states.[vii] Although the initiative was not implemented due to both Israeli and Arab criticisms, it has remained on the table and has subsequently been re-endorsed in both 2007[viii] and 2017[ix] by the Arab League.[x] After the KSA joined the World Trade Organisation in 2005, this resulted in the Kingdom downgrading its economic embargo against Israel, and second and third-level boycotts on exchanges with Israeli-headquartered businesses and businesses affiliated with Israel were removed.[xi]
A Convergence of Interests
The Lebanon War of 2006 exemplified how Saudi-Israeli interests have converged over perceived threats from Iran. As war erupted between Israel and Hezbollah (an Iranian-sponsored Shi’a terrorist organisation), the KSA criticised Hezbollah for “bringing calamity on Lebanon” and contended that its conduct is “religiously illegal.”[xii] Iran has posed a threat to the KSA since the 1979 revolution that brought to power a regime seeking to expand Iran’s hegemony in the Persian Gulf. Iran has inserted itself into the Palestinian-Israeli conflict by supporting proxies such as Hezbollah, Islamic Jihad and Hamas. By doing so, Tehran hopes to open additional military fronts against Israel as well as exploitatively highlight “the hypocrisy of Arab governments” who offer rhetorical rather than materiel support to the Palestinians.[xiii] Iran has been the instigator of most of the conflicts near Israel’s borders, and its interest in developing a nuclear program is a major threat to Israel as well as the KSA. Accordingly, differences between Israel and the KSA regarding peace with the Palestinians and the API were overshadowed by the common threat from Iran, which was the main factor that crystallised a tacit security regime (TSR) between the two countries.[xiv] Nevertheless, relations between the two parties prior to the Arab Spring were highly clandestine in nature, with exception of media leaks such as the WikiLeaks documents released in 2010 demonstrating discreet meetings between officials from the KSA and Meir Dagan, head of the Mossad.[xv]
Following the Arab Spring in 2011, the opportunity to intensify covert relations and solidify a TSR between Israel and the KSA heightened owing to an increased convergence of interests. With the emergence of power vacuums in the region, Iran’s hegemonic ambitions intensified, and it was provided with the opportunity to expand its influence.[xvi] Furthermore, America’s evident retrenchment from the Middle East under the Obama and Trump administrations was a complementing factor that increased the need for Saudi-Israeli cooperation.[xvii] For instance, President Barack Obama’s efforts to negotiate a deal with Iran without Arab involvement and President Donald Trump’s promise to end America’s status as “the world’s policeman” rang alarm bells in Gulf Cooperation Council countries, in general, and the KSA, in particular. The Gulf states came to believe that the US is no longer devoted to their security and that they are no longer under the “protective umbrella of the US.”[xviii]
Furthermore, the Joint Comprehensive Plan of Action (JCPOA), signed between the P5+1 and the EU and Iran in 2015, was a major concern for Israel and the KSA and, therefore, aided their alignment, as the deal lifted the sanctions that aimed to isolate Iran and deter advancement of its nuclear program.[xix] Accordingly, covert exchanges increased between Israel and the KSA with the aim of pressuring the US; in 2018, the US did in fact withdraw from the nuclear deal and reimposed sanctions on Iran.[xx] Nevertheless, the remaining signatories of the deal continued to support the JCPOA and have worked towards establishing economic mechanisms to “circumvent American sanctions.”[xxi] In addition, the KSA—aware of its constrained military and technological abilities—began perceiving Israel as a “potential partner” due to its advanced technological skills and professional military.[xxii] Likewise, Qatar and Turkey’s alignment (along with Iran) had also been mutually perceived by Israel and the KSA as a threat. From the Kingdom’s point of view, Qatar’s relations with Iran threaten the KSA-led Sunni axis and could facilitate the creation of a trilateral coalition, threatening the KSA’s ambitions of regional leadership.[xxiii]
The TSR between the KSA and Israel expanded following the Arab Spring to secret and non-confidential meetings between officials from the two countries, as well as to cooperation in security sectors.[xxiv] Officially, Israel and the KSA are considered adversaries; yet, in reality, they are affiliates with issue areas of common interest. Nevertheless, the Kingdom has been more cautious than Israel in its public statements, refraining from acknowledging its clandestine relations with Israel, while Israel openly contends that it has friendly relations with the KSA.[xxv] Nevertheless, cooperation in areas of common interest does not rule out the possibility of areas of disagreement. To elaborate, the lack of advancements regarding the Palestinian question is a major point of disagreement and remains an obstacle in the development of official relations between the KSA and Israel. This barrier may keep relations constrained to a TSR. Clearly, clandestine relations between Israel and the KSA were taking place while the latter was supporting UN Resolution 2334, which condemned Israeli settlements in the West Bank, and Saudi Grand Mufti Abdulaziz al-Shaykh was contending that “ISIS was in reality an adjunct of the Israeli army.”[xxvi]
While arms deals and intelligence exchanges are highly confidential and unknown to the public, one Israeli-Saudi arms deal was disclosed in 2015 when an American staff member of Israel’s Elbit Systems Ltd. was found dead after travelling to the Kingdom to inspect electronic equipment for Elbit-created missiles.[xxvii] Additionally, it has been reported that the KSA is in discussions with Israel to build a gas pipeline to Eilat for exporting Israeli natural gas. This would facilitate exports to the Kingdom and the West as well as counter potential Iranian blockades in the Straits of Hormuz and Bab al-Mandeb in the Red Sea.[xxviii] Furthermore, Anwar Eshki (a former Saudi General) and Dore Gold (Director-General of Israel’s Ministry of Foreign Affairs), although in an unofficial capacity, have also held several clandestine meetings dedicated to addressing the challenge posed by Iran.[xxix] Eshki led a Saudi delegation to Israel in 2016 arguing that “The situation has changed. We can easily single out common enemies.”[xxx] In 2017, Israel’s Minister of Energy further affirmed Israeli-Saudi covert exchanges regarding Iran. In addition, the Chief of Staff of the Israel Defense Forces asserted in an interview with the Saudi press that the parties fully agree on the matter of Iran, and he offered to share intelligence regarding the matter.[xxxi]
To complement the Saudi leadership’s new stance on Israel, the KSA has altered how the country’s media covers Israel and Jews—an “open yet subtle signal” to engender domestic consensus.[xxxii] Following the death of four Israelis in a shooting attack in Tel Aviv, Saudi media—including the famous Pan-Arab Al-Arabiya channel—condemned the attack; Saudi journalists explicitly showed solidarity, claiming that their support for Palestinians should not stop them from expressing condolences for the murder of innocent Israelis.[xxxiii] Moreover, during Eshki’s visit to Israel, Saudi media published several articles “toning down anti-Semitism.”[xxxiv] Such efforts were nevertheless criticised by the Saudi public.[xxxv]
Implications for the Palestinian Cause
The prominent argument used to justify the subordination of the Palestinian cause to the Saudi foreign policy agenda—in addition to the benefits of the TSR with Israel—is the division among Palestinians and the weakening of Palestinian leaders.[xxxvi] For instance, while Palestinians and their supporters have perceived Arab normalisation with Israel as a betrayal of the Palestinian cause, Palestinian Authority President Mahmoud Abbas failed to push for the condemnation of the Israeli-Emirati normalisation deal by the Arab League.[xxxvii] The divergence of Palestinians’ political alignments and antagonism between Hamas and the Palestinian Authority, along with the limited ability of Palestinian national movements to impact regional politics, have contributed to blurring the “red line” that prevents Arab states from associating with Israel.[xxxviii] Moreover, the fragmentation of Arab national identity and Arab unity resulted in a shift towards focusing on each individual state’s national interest and away from prioritising the Palestinian cause. This has been the case with the KSA, which in response to threats from Iran has initiated security cooperation with Israel to acquire military support, intelligence, arms and further extend such cooperation to non-security sectors.[xxxix]
Thus far, the Saudi-Israeli TSR has come at the detriment of the Palestinian cause. Indeed, it has been argued that cooperation between the two parties can sway Israeli-Palestinian peace negotiations in Israel’s favour—in contrast to the Palestinians’ standing being theoretically enhanced when it is backed by Arab states.[xl] Although the KSA continues to support Palestinians rhetorically, in reality, its TSR with Israel has weakened its commitment. This was evident in the KSA’s decision to attend a White House conference on the humanitarian situation in Gaza in 2018 along with Israeli representatives and without Palestinian representatives, despite previous Saudi abstention from participating in any assembly on Palestinian matters that does not include Palestinian representation.[xli]
Furthermore, Crown Prince Mohammed Bin Salman is plainly adopting a malleable position regarding the Palestinian question. The Crown Prince explicitly recognised the rights of both Palestinians and Israelis to their own land, and he reportedly insisted that Iran is more of a priority than the Palestinians for his country.[xlii] As a result, the Israeli argument that “there is no Palestinian partner to negotiate with” was adopted by Saudi decision-makers, and the Palestinian cause became a debatable issue, rather than a crucial matter, among the public. In a poll conducted by the Arab Youth Survey, the issue of Palestinians was downgraded from being the third most important issue in 2012 to the eighth in 2017.[xliii] Moreover, if Saudi-Israeli relations were to become official, this would motivate other Arab states to cooperate with Israel, since the leader of the Muslim World would have recognised Israel.[xliv]
Nevertheless, there are limitations on the KSA that hinder the development of its TSR with Israel into an official full-scale relationship. It is vital for the KSA to secure its status as the guardian of Islam’s holy sites, which makes protecting Jerusalem—a main component of the Palestinian cause—a religious responsibility and essential to maintaining its legitimacy within the Islamic world.[xlv] Therefore, if the TSR with Israel were to shift to official relations, not only would the KSA’s standing be undermined, but it would also face consequences at the domestic political level because the Palestinian cause is still “emotive for Arab publics.”[xlvi] Accordingly, one pragmatic scenario might include the KSA continuing to develop “low-key relations” for its security objectives while maintaining the Kingdom’s role in the Arab world.[xlvii] For example, the KSA’s passivity towards, and implicit acceptance of, Arab states’ peace agreements with Israel is another means of indirectly advancing relations.
As relations deepen between the KSA and Israel, however, they have also been thrust into the open. This may negatively impact the KSA’s national image and allow other regional states to compete with it for hegemony.[xlviii] Accordingly, the KSA’s position is in fact being weakened as Turkey seeks regional leadership. In 2017, Turkey called an emergency meeting of the Organisation of Islamic Cooperation to discuss the situation in Gaza and also hosted the meetings in 2018.[xlix]
Therefore, for the time being, it is apparent that the KSA will not expand its relations beyond the TSR as long as the Palestinian-Israeli issue remains stagnant. Instead, Riyadh will continue to benefit from its secret cooperation with Israel while preserving its regional legitimacy.[l]
[i] Prittie, Terence and Nelson, Walter Henry, “The Economic War against the Jews”. London: Secker and Warburg, 1978.
[ii] Podeh, Elie. “From Fahd to ‘Abdallah: The Origins of the Saudi Peace Initiatives and Their Impact on the Arab System and Israel.” Hebrew University of Jerusalem, Harry S. Truman Institute for the Advancement of Peace, Gitelson Peace, 24 (41), 2003.
[iii] Fahd Plan, 1981. https://www.un.org/unispal/document/auto-insert-209344.
[iv] “A Look at Fahd’s 1981 Mideast Peace Plan.” Associated Press. 01 August 2005. https://apnews.com/article/ffb68bc03b0433f480266cf834c81769.
[v] Kostiner, Joseph. “The Marginal Peace: The Attitudes of the Persian Arabian Gulf States towards Israel and the Peace Process,” Tami Steinmetz Center for Peace Research, 2008.
[vi] Shipler, David K. “Israel Rejects Arab Plan, Terming It Destructive.” The New York Times. 11 September 1982. https://www.nytimes.com/1982/09/11/world/israel-rejects-arab-plan-terming-it-destructive.html.
[vii] Nonneman, Gerd. “Determinants and Patterns of Saudi Foreign Policy:’Omnibalancing’ and ‘Relative Autonomy’ in Multiple Environments.” Saudi Arabia in the balance: Political economy, society, foreign affairs, 220, 315-51, 2005.
[viii] Fattah, Hassan M. “Heads of Arab States Prod Israel to Embrace Peace Offer.” The New York Times. 30 March 2007. https://www.nytimes.com/2007/03/30/world/middleeast/30saudi.html.
[ix] Laub, Karin. “At White House, Jordan king to present Arabs’ view on Peace.” The Times of Israel. 04 April 2017. https://www.timesofisrael.com/at-white-house-jordan-king-to-present-arabs-view-on-peace/.
[x] Teitelbaum, Joshua. “The Arab peace initiative: A primer and future prospects.” Jerusalem: Jerusalem Centre for Public Affairs, 2009. http://jcpa.org/article/the-arab-peace-initiative-a-primer-and-future-prospects.
[xi] Washington Times, “Amity with Israel opens TWO door,” 2005. https://www.washingtontimes.com/news/2005/nov/12/20051112-123734-4633r/.
[xii] Podeh, Elie. “Saudi Arabia and Israel: From secret to public engagement, 1948–2018.” The Middle East Journal, 72(4), 563-586, 2018.
[xiii] Sachs, Natan and Huggard, Kevin. “Israel in The Middle East The next two decades.” Middle East, 2020.
[xiv] Melman, Yossi. “Iran’s Response to Second Lebanon War Is Israel’s Gain.” Haaretz, 17 July 2011. https://www.haaretz.com/2011-07-17/ty-article/irans-response-to-second-lebanon-war-is-israels-gain/0000017f-e1d1-d804-ad7f-f1fb6ba50000.
[xv] Mahnaimi, Uzi and Baxter, Sarah. “Saudis Give Nod to Israeli Raid on Iran.” The Times (UK), 5 July 2009. www.thetimes.co.uk/article/saudis-give-nod-to-israeli-raid-on-iran-qp2blhgk36c.
[xvi] Guzansky, Yoel and Lindenstrauss, Gallia. “The Emergence of the Sunni Axis in the Middle East.” Strategic Assessment, 16(1), 37-48, 2013.
[xvii] Lepeska, David. Obama and the Middle East: Why the US is Disengaging. The National, 27 Jan. 2012. https://www.thenationalnews.com/arts-culture/books/obama-%20and-the-middle-east-why-the-us-is-disengaging-1.404554; Sly, Liz. “In the Middle East, Russia is Back.” The Washington Post, 5 Dec. 2018. https://www.washingtonpost.com/world/in-the-middle-east-russia-is-back/2018/12/04/e899df30-aaf1-11e8-9a7d-cd30504ff902_story.html.
[xviii] Samuels, Brett. “Trump: We don’t want to be the policeman of the world.” The Hill, 30 April 2018. https://thehill.com/homenews/administration/385521-trump-we-dont-want-to-be-the-policemen-of-the-world/.
[xix] Wong, Edward. “Trump Imposes New Sanctions on Iran, Adding to Tensions.” The New York Times, 24 June 2019. https://www.nytimes.com/2019/06/24/us/politics/iran-sanctions.html.
[xx] Turak, Natasha. “Europe, Russia and China join forces with a new mechanism to dodge Iran sanctions.” CNBC, 25 Sep. 2018. https://www.cnbc.com/2018/09/25/eu-russia-and-china-join-forces-to-dodge-iran-sanctions.html.
[xxi] Kirkpatrick, David and Sanger, David. “Iran Announces New Breach of Nuclear Deal Limits and Threatens Further Violations.” The New York Times, 7 July 2019. https://www.nytimes.com/2019/07/07/world/middleeast/iran-nuclear-limits-breach.html.
[xxii] Ferziger, Jonathan and Bahgat, Gawdat. “Israel’s Growing Ties with the Gulf Arab States.” Atlantic Council, 2020. https://www.atlanticcouncil.org/wp-content/uploads/2020/07/Israel%E2%80%99s-Growing-Ties-with-the-Gulf-Arab-States.pdfhttps://www.atlanticcouncil.org/wp-content/uploads/2020/07/Israel%E2%80%99s-Growing-Ties-with-the-Gulf-Arab-States.pdf.
[xxiii] Frantzman, Seth. “Turkey’s power-play in Qatar leads to warmer relations with Iran.” The Jerusalem Post, 1 July 2017. https://www.jpost.com/arab-israeli-conflict/turkeys-power-play-in-qatar-leads-to-warmer-relations-with-iran-498468; Guzansky, Yoel and Michael, Kobi. “Israel’s Qatari Dilemma.” Institute for National Security Studies, INSS Insight, 1034, 2018. https://www.inss.org.il/publication/israels-qatari-dilemma/.
[xxiv] Bowman, Bradley, Lauren Harrison and Ryan Brobst. “Saudi Arabia and Israel Tiptoe Toward Overt Security Cooperation.” Military.com. 6 November 2021. https://www.military.com/daily-news/opinions/2021/11/06/saudi-arabia-and-israel-tiptoe-toward-overt-security-cooperation.html
[xxv] Kahana, Ariel. “PM: Israel maintaining overt, covert ties with Arab leaders.” Israel Hayom, 19 June 2019. https://www.israelhayom.com/2019/06/19/pm-israel-maintaining-overt-covert-ties-with-arab-leaders/.
[xxvi] Jones, Clive and Guzansky, Yoel. “Israel’s Relations with the Gulf States: Toward the Emergence of a Tacit Security Regime?” Contemporary Security Policy, 38 (3): 398–419, 2017.
[xxvii] McCormack, Kathy. “Mystery surrounds Saudi Arabia death of Israel-Linked defense contractor.” Times of Israel, 15 January 2019. https://www.timesofisrael.com/mystery-surrounds-saudi-arabia-death-of-israel-linked-defense-contractor/.
[xxviii] Musmar, Frank. “Saudi Arabia and Israel: who needs whom.” The Algemeiner, 2019. https://www.algemeiner.com/2019/12/13/saudi-arabia-and-israel-who-needs-whom/.
[xxix] Wittes, Tamara Cofman. “How Important is Saudi-Israeli Track Two Diplomacy?” Brookings/Markaz Blog, 6 June 2015. https://www.brookings.edu/blog/markaz/2015/06/06/how-important-is-saudi-israeli-track-two-diplomacy/.
[xxx] Eldar, Akiva. “What Saudi Arabia Can Offer Israel.” Al-Monitor, 28 July 2016. https://www.al-monitor.com/originals/2016/07/saudi-arabia-egypt-visit-jerusalem-arab-peace-initiative.html.
[xxxi] Black, Ian. “Why Israel is quietly cosying up to Gulf monarchies.” The Guardian, 19 March 2019. https://www.theguardian.com/news/2019/mar/19/why-israel-quietly-cosying-up-to-gulf-monarchies-saudi-arabia-uae.
[xxxii] Jones, Clive and Guzansky, Yoel. “Israel’s Relations with the Gulf States: Toward the Emergence of a Tacit Security Regime?” Contemporary Security Policy, 38 (3): 398–419, 2017.
[xxxiii] Groisman, Maayan. “Palestinians Celebrate Terror Attack in Tel Aviv, Saudis Strongly Condemn.” The Jerusalem Post, 9 June 2016. https://www.jpost.com/arab-israeli-conflict/palestinians-celebrate-terror-attack-in-tel-aviv-saudis-strongly-condemn-456344.
[xxxiv] Ulrichsen, Kristian Coates. “Israel and the Arab Gulf States: Drivers and Directions of Change.” Center for the Middle East, 2016. https://scholarship.rice.edu/handle/1911/91811.
[xxxv] Fakhro, Elham. “Selling Normalization in the Gulf.” Middle East Research and Information Project, 2021. https://merip.org/2021/06/selling-normalization-in-the-gulf/.
[xxxvi] Dorsey, James. “Will They or Won’t They? Saudi Recognition of Israel Is the $64,000 Question.” BESA Center Perspectives Paper, 2020. https://besacenter.org/will-they-or-wont-they-saudi-recognition-of-israel-is-the-64000-question/.
[xxxvii] Al-Monitor. “Arab League Refuses to Back Palestinians in Rebuke of Israel-UAE Deal,” 2020. https://www.al-monitor.com/originals/2020/09/arab-league-palestinian-uae-israel-normalization-condemn.html
[xxxviii] Heller, Aron. Arab leaders play down Palestinian issue in leaked video. Associated Press, 14 February 2019. https://apnews.com/article/12eab3b948bb415e9f6300601be9939b.
[xxxix] Niu, Song and Wu, Tongyu. “Changes and Trends in the Current Relations Between Saudi Arabia and Israel.” Asian Journal of Middle Eastern and Islamic Studies, 15(2), 172-188, 2021.
[xl] Enotus, Aadam. “Donald Trump’s New World Order.” The New Yorker, 11 June 2019. https://www.newyorker.com/magazine/2018/06/18/donald-trumps-new-world-order.
[xli] Rynhold, Jonathan and Yaari, Michal. “The transformation of Saudi-Israeli relations.” Israel Affairs, 26(6), 799-818, 2020.
[xlii] Ulrichsen, Kristian Coates. “Palestinians Sidelined in Saudi-Emirati Rapprochement with Israel.” Journal of Palestine Studies, 47(4), 79-89, 2018; Hubbard, Ben. “MBS: The rise to power of Mohammed Bin Salman.” Crown, 2021.
[xliii] Pollock, David and Cleveland, Catherine. “Comparing Arab Polls on Trump, U.S. Policy, Israel, Iran and More.” Fikra Forum, 9 May 2019. https://www.washingtoninstitute.org/policy-analysis/comparing-arab-polls-trump-us-policy-israel-iran-and-more.
[xliv] Zaken, Dan. “Saudi Arabia opens its doors to Israeli Arabs.” Globes, 21 May 2019. https://en.globes.co.il/en/article-saudi-arabia-opens-its-doors-to-israeli-arabs-1001286453.
[xlv] Abadi, Jacob. “Saudi Arabia’s rapprochement with Israel: the national security imperatives.” Middle Eastern Studies, 55(3), 433-449, 2019.
[xlvi] Furlan, Marta. “Israeli–Saudi Relations in a Changed and Changing Middle East: Growing Cooperation?” Israel Journal of Foreign Affairs, 13(2), 173-187, 2019.
[xlvii] Musmar, Frank. “Saudi Arabia and Israel: who needs whom.” The Algemeiner, 2019. https://www.algemeiner.com/2019/12/13/saudi-arabia-and-israel-who-needs-whom/
[xlviii] Chehab, Ahmad. “Israel and the Gulf States: Clandestine Contacts.” Academia, 2015. https://www.academia.edu/37741242/ISRAEL_AND_THE_GULF_STATES_CLANDESTINE_CONTACTS.
[xlix] DW News. “Turkey Calls for an Emergency Meeting of the Organization of Islamic Cooperation on Jerusalem,” 2017. https://www.dw.com/ar/تركيا-تدعو-إلى-اجتماع-طارئ-لمنظمة-التعاون-الإسلامي-بشأن-القدس/a-41671831.
[l] Guzansky, Yoel. “Israel and the Arab Gulf states: from tacit cooperation to reconciliation?” Israel Affairs, 21:1, 131-147, 2015. https://www.tandfonline.com/doi/abs/10.1080/13537121.2014.984424.