English: The "triangle of Kyiv, Chernihiv and Pereyaslavl" in 1132, also known as the "Kyiv–Chernihiv–Pereiaslav triangle", the "triangle of Kiev, Chernigov, and Pereiaslavl’", or "Kievan triangle". According to Soviet historian Arseniy Nikolaevich Nasonov, “Russkaia zemlia” i obrazovanie territorii drevnerusskogo gosudarstva. Istoriko-geograficheskoe issledovanie (Moscow: Nauka, 1951), pp. 216–20, these three urban centres and their principalities formed the core area of what contemporaneous Rus' sources (since the late 11th century, through the 12th century, until at least the early 13th-century Kyivan Chronicle) identified as "Rus'", or "the Rus' Land". Nasonov posited, for example, that when these texts said someone travelling from Vladimir-Suzdal in the northeast, Velikiy Novgorod in the north, or Galicia-Volhynia (Halych-Volyn) in the southwest, was "going to Rus'", the context indicated that this usually meant the area of the cities of Kyiv (Kiev), Chernihiv (Chernigov) and Pereyaslavl (Pereiaslav) on the Middle Dnipro (Dnieper). The area designated as "Rus' (Land)" would only expand later to encompass other parts of the Rurikid/Volodimerovichi realm, or the whole of Kievan Rus' (Kyivan Rus'). In addition, by the middle of the 14th century, the term "Rus' Land" had taken on a new, third meaning, no longer referring to the Kievan triangle or all of former Kievan Rus', but to the Suzdalian principalities in the northeast, later specifically Muscovy (the Grand Duchy of Moscow).

Several scholars such as Rybakov (1953), Cherepnin (1958), Tikhomirov (1947) and Artamonov (1962) accepted Nasonov's theory. Opponents such as Likhachev and Soloviev claimed that the term "Rus' (Land)" had already acquired a broader political meaning encompassing all East Slavic Kievan Rus' territories earlier that Nasonov proposed.

• Plokhy, Serhii (2006) The Origins of the Slavic Nations: Premodern Identities in Russia, Ukraine, and Belarus, Category:New York: Cambridge University Press, pp. 37–39, 49, 70–71 ISBN: 978-0-521-86403-9.
• Halperin, Charles J. (17 February 2016). "A Tatar interpretation of the battle of Kulikovo Field, 1380: Rustam Nabiev". Nationalities Papers 44 (1): 12. DOI:10.1080/00905992.2015.1063594. ISSN 0090-5992.
• Halperin, Charles J. (2022) The Rise and Demise of the Myth of the Rus' Land, Лідс: Arc Humanities Press, pp. 7, 18, 20, 41, 58 ISBN: 9781802700565.