In its original form this book was written as a doctoral thesis for the Courtauld Institute of Art, and I am deeply indebted to my two supervisors, Prof. Sir Anthony Blunt and Prof. Douglas Cooper, for all their help and advice. While I was writing the thesis my researches were aided by a grant from the Research Fund of the University of London. The many private collectors in Europe and America who allowed me to see Cubist works in their possession are too numerous to mention; I am particularly grateful to those who have given me permission to reproduce paintings from their collections. Of the officials of the libraries, museums and galleries who have helped me, I should like especially to mention Mr. Alfred Barr, Jr. and Mr. William S. Lieberman of the Museum of Modern Art, New York. I am extremely grateful, too, to M. Daniel H. Kahnweiler, to Mme. Juliette Roche Gleizes and to Mme. Sonia Terk Delaunay for all the time they spared me, and for letting me see unpublished and generally inaccessible documents in their possession. I would also like to thank Air. John Richardson for calling my attention to many important points, in particular to the discovery of the very rare 'mathematical' drawings by Gris. Finally I should like to thank Mr. James Joll for the advice and encouragement he has given me at every stage of the work.
Z refers to C. Zervos, Picasso, Vols 1-6, Paris 1932-54.