1. A. O. Gel'fond, ?On the algebraic independence of transcendental numbers of certain classes,? Usp. Mat. Nauk,4, No. 5, 14?48 (1949).
2. A. O. Gel'fond, Transcendental and Algebraic Numbers [in Russian], Gostekhizdat, Moscow (1952).
3. D. W. Brownawell, ?The algebraic independence of certain numbers related by the exponential function,? J. Number Theory,6, No. 1, 22?31 (1974).
4. M. Waldschmidt, ?Solution d'un problème de Schneider sur les nombres transcendants,? C. R. Acad. Sci.,271, No. 15, A697-A700 (1970).
5. M. Waldschmidt, ?Solution du huitième problème de Schneider,? J. Number Theory,5, No. 3, 191?202 (1973).