Jubilees 8:29
28 It goes to the edge of the Tina River toward the northeast until it reaches the bank of its waters toward the mountain range of Rafa. It goes around the north. 29 This is the land that emerged for Japheth and his children as his hereditary share which he would occupy for himself and his children throughout their generations forever: five large islands and a large land in the north. 30 However, it is cold while the land of Ham is hot. Now Shem's land is neither hot nor cold but it is a mixture of cold and heat.
1 Enoch 77:8
6 Two of these rivers come from the north and empty their waters into the Erythraean Sea in the east. 7 The remaining four originate from the north and flow into their respective seas; two into the Erythraean Sea and two into the Great Sea, with some ending in the desert. 8 I saw seven great islands, two on the mainland and five in the Great Sea.
Notes and References
"... From here the border again reaches familiar territory, going “to the edge of the Tina River toward the northeast until it reaches the banks of its waters toward the mountain range of Rafa. It goes around the north” (8:28). The next verse adds that Japheth’s eternal inheritance includes “five large islands and a large land in the north.” Four great islands in the Great Sea are also mentioned as part of Japheth’s son Tiras’ allotment in Jubilees 9:13. Since Shem has already been allotted the “islands of Kaftur”, we may deduce that these four are likely Crete, Sicily, Sardinia and Corsica. Based on a reference to “the islands and the shores of the islands” in the description of Madai’s portion (9:9), Hölscher and Alexander have suggested that the fifth great island of 8:28 is Britain, or the British Isles more generally. These islands were indeed known to the Ionians, making this identification plausible. (Charles, in The Book of Jubilees, p. 75, also noted the reference to islands in 1 Enoch 77:8) ..."
Machiela, Daniel A. The Genesis Apocryphon (1Q20): A Reevaluation of Its Text, Interpretive Character, and Relationship to the Book of Jubilees (pp. 243-244) University of Notre Dame, 2007