G.D. Demopoulos (1971).
H. Reichardt (1971).
A series of lectures given at the National Technical University of Athens (1970).
J. Rothenberg (1967).
R. Eisner (1966).
G. Weisser (1965, also in Greek).
A.A. Fatouros (1965).
K.J. Arrow (1965).
J. H. Merryman (1965, also in Greek).
G.C. Archibald (1964).