FOREWORD 
For several reasons, the publication of this report was postponed for several years. 
Its contents were summarized at the time of this author’s oral presentation at DTRC in 
July 1985, reflecting the state-of-the-art up to 1984. The manuscript of the written 
version was completed in August 1987 and is now to be published five years later in 
1992. During these years the state-of—the—art has made considerable progress, and this 
author finds the “review” to be insufficient, especially in Part III because of the recent 
works of several researchers. In order to update the report this author has added a 
“Supplement of References,” (Refs. 101-124) listing publications that have appeared 
since 1984, together with some other publications that he had failed to refer to in the 
original manuscript. 
