This book was first published in 1960 as No. 5 of volume 49 of the reports of the Forestry Research Institute of Sweden.

He was at the same time a doctor's thesis in mathematical statistics at the University of Stockholm. In the second edition, a number of erroneous errors and other errors were corrected.

Author and Subject Index added. Finally, comments on a new footnote comment on the subsequent development of the topics addressed in the book.

BERTIL MATERN March rc6 Acknowledgments This message was facilitated by generous assistance to many people and institutions. I would like to express my sincere gratitude to my teacher, Prof.

Harald Kramter, who is now an adviser to the Swedish universities for his invaluable assistance and encouragement. A sincere thanks are also given to Professor Oliv Greener for reading the first edition of the manuscript and giving valuable advice.

The thesis was prepared in two separate periods on a large scale. Preliminary draft of the chapter.

2 was written in 1948, while the remaining parts were completed in 1959-1960. The work stems from the problems I discussed in a publication in 1947.

The problems were set for me by Professor Manfred Nesselund, former president of the Swedish Institute of Forestry Research, now governor of Norbotten County. It gives me great pleasure to express my gratitude to Professor Nislund for his encouragement and interest in my work..