Truss (1976), p. 273; Howard & Rubin (1998), pp. 20, 243; compare Lévy (1979), Exercise IX.2.18. Truss, J. (1976), "Some cases of König's lemma", in Marek, V. Wiktor; Srebrny, Marian; Zarach, Andrzej (eds.), Set Theory and Hierarchy Theory a Memorial Tribute to Andrzej Mostowski, Lecture Notes in Mathematics, vol. 537, Springer, pp. 273–284, doi:10.1007/BFb0096907, ISBN978-3-540-07856-2, MR0429557 Howard, Paul; Rubin, Jean (1998), Consequences of the Axiom of Choice, Mathematical Surveys and Monographs, vol. 59, Providence, RI: American Mathematical Society Lévy, Azriel (1979), Basic Set Theory, Springer, ISBN3-540-08417-7, MR0533962; reprint, Dover, 2002, ISBN0-486-42079-5.
Truss (1976), p. 273; Howard & Rubin (1998), pp. 20, 243; compare Lévy (1979), Exercise IX.2.18. Truss, J. (1976), "Some cases of König's lemma", in Marek, V. Wiktor; Srebrny, Marian; Zarach, Andrzej (eds.), Set Theory and Hierarchy Theory a Memorial Tribute to Andrzej Mostowski, Lecture Notes in Mathematics, vol. 537, Springer, pp. 273–284, doi:10.1007/BFb0096907, ISBN978-3-540-07856-2, MR0429557 Howard, Paul; Rubin, Jean (1998), Consequences of the Axiom of Choice, Mathematical Surveys and Monographs, vol. 59, Providence, RI: American Mathematical Society Lévy, Azriel (1979), Basic Set Theory, Springer, ISBN3-540-08417-7, MR0533962; reprint, Dover, 2002, ISBN0-486-42079-5.