This book is a result of many years' interest in the economic theory of pro­ duction, first aroused by the reading of Professor ERICH SCHNEIDER'S classic Theorie der Produktion. A grant from the Danish-Norwegian Foundation made it possible for me to spend six months at the Institute of Economics, University of Oslo, where I became acquainted with Professor RAGNAR FRISCH'S penetrating pioneer works in this field and where the plan of writing the present book was conceived. Further studies as a Rockefeller fellow at several American univer­ sities, especially an eight months' stay at the Harvard Economic Research Pro­ ject, and a visit to the Unione Industriale di Torino have given valuable impulses. For these generous grants, and for the help and advice given by the various institutions I have visited, I am profoundly grateful. My sincere thanks are also due to the University of Copenhagen for the ex­ ceptionally favourable working conditions which I have enjoyed there, and to the Institute of Economics-especially its director, Professor P. N0RREGAARD RASMUSsEN-for patient and encouraging interest in my work. I also wish to thank the Institute's office staff, Miss G. SUENSON and Mrs. G. STEN0R, for their constant helpfulness, and Mrs. E. HAUGEBO for her efficient work in preparing the manuscript, which was completed in the spring of 1965.