1. Handbook of Mathematical Functions;Abramowitz,1972
2. Positive Solutions of Differential, Difference and Integral Equations;Agarwal,1999
3. S.N. Askhabov, M.A. Betilgiriev, Nonlinear convolution type equations, in: Seminar Analysis, Berlin, 1989/1990, pp. 1–30 (Karl-Weierstrass-Inst. Math., Berlin, 1990).
4. Monotonie: Lösbarkeit und Numerik bei Operatorgleichungen;Bohl,1974
5. Hilbert's metric and positive contraction mappings in a Banach space;Bushell;Arch. Rational-Mech. Anal.,1973