1. R. M. Robinson,A Report on Primes of the Form k·2 n+1 and on Factors of Fermat numbers, Proc. Am. Math. Soc., vol. 9, 1958, p. 673–681.
2. C. P. Wrathall,New Factors of Fermat Numbers, Math. Comp., vol. 18, 1964, p. 324–325.
3. H. Riesel,Some Factors of the Numbers $$G_n = 6^{2^n } + 1$$ and $$H_n = 10^{2^n } + 1$$ , Math. Comp., vol. 23, 1969, p. 413–415.