The Interstellar Medium : Proceedings of the NATO Advanced Study Institute held at Schliersee, Germany, April 2-13, 1973 : Springer : 9789027704177 : 9027704171 : 31 Mar 1974 : In recent years it has become apparent that con­ tributions to our knowledge about the interstellar medium are made by practically all forms of astronomy ranging from radio- to gamma ray observations, and from cosmic ray measurements. It was thus thought fruitful to arrange for an interdisciplinary meeting of astron­ omers from the various fields of investigation, and of high energy astrophysicists. This meeting took place at Schliersee (Bavaria) from April 2 to 13, 1973. Lectures and some of the discussions held during that Advanced Study Institute are reproduced here. unfortunately, no manuscripts of the two lectures about infrared and cosmic ray observations were re­ ceived and these are thus not available here. However, it was thought to be more important to proceed now with the publication. The organisers a