1. W. Ljunggren. Zur Theorie der Gleichung x2 +1 = Dy4. Avh. Norske Vid. Akad. Oslo1 No.5 (1942), 1–27.
2. M. Mignotte and M. Waldschmidt. Linear Forms in Two Logarithms and Schneider’s Method III. Ann. Fac. Sci. Toulouse, V. Sér., Math. 1989, Spec. Issue, 43–75.
3. L.J. Mordell. Diophantine Equations. Academic Press, New York-London 1969.
4. R. Steiner andN. Tzanakis. Simplifying the Solution of Ljunggren’s Equation x2 + 1 = 2y4 J. Number Theory3 No.2 (1991), 123–131.