. Augmented by a 2-page introductory Preface written in September 1997, this manuscript consists of Chapters 8, 9 and 10 of Warfield's out of print book Societal Systems, using original page numbers, from p. 208 to p. 284. These chapters contain the essential mathematics needed for understanding Interpretive Structural Modeling and for writing the software. There is a front cover and a back cover page which are used when printing the document which is now an IASIS REPORT. The format used in Societal Systems has been reproduced as closely as possible, with matching font, so that the pages resemble the original 1976 edition. This material (and more) from Societal Systems has been used often in Warfield's classes, principally in the Mathematics of Modeling short courses, but elsewhere as well. For a long time he used photocopies of the 1976 Wiley publication for his classroom handouts, until software improved to the point that retyping the pages into a computer document became feasible. Sandra did some of the typing in 1994, and Rose Warfield tried to do some more in 1995 and 1996, but the math notations and format style were not easy on wordperfect 5. Warfield finally began working on the chapters himself, and finished the reproduction of Chapters 8, 9 and 10 in 1997. (Warfield still has imperfect secretary's copies of Societal Systems chapters 11,12,13 and 14 on the computer and he intends to edit and reproduce them, also, in the future.. Warfield plans to eventually produce a book on mathematics of structural modeling, of which this monograph will become a part. R.w. circa 2000