1. Adem, J. (1980-81) ‘On the Hurwitz problem over an arbitrary field I-II’, Bol. Soc. Mat. Mexicana (2) 25, 29–51.
2. Adem, J. (1980-81) ‘On the Hurwitz problem over an arbitrary field I-II’, Bol. Soc. Mat. Mexicana (2) 26, 29–41.
3. Andreotti, A. and Tomassini, G. (1978) Spazi vettoriali topologici, Pitagora Editrice, Bologna.
4. Banach, S. (1932) Théorie des opérations linéaires (Monografje Matematyczne 1), Z subwencji Funduszu Kultury Narodowej, Warszawa.
5. Griffiths, P. and Harris, J. (1978) Principles of Algebraic Geometry, J. Wiley & Sons, New York-Chichester-Brisbane-Toronto.