By Avery, H..
Barcelona : Reverté, 1974

By Babor, José.
Barcelona : Marín, 1968

By Castellan, Gilbert.
Bogotá : Fondo Educativo Interamericano, 1981 9686630449

By Mandleberg, J..
Zaragoza : Acribia, 1981

By Metz, Clyde.
Bogotá : McGraw-Hill Latinoamericana, 1977 0070909385

By Price, Nicholas.
Oxford : Clarendon Press, 1979

By Smith, A..
London : McGraw-Hill, 1968