that about 100 journals are required to yield fifty In 1957, the Thermophysical Properties Research percent. But that other fifty percent! It is scattered Center (TPRC) of Purdue University, under the leadership of its founder, Professor Y. S. Touloukian, through more than 3500 journals and other docu began to develop a coordinated experimental, ments, often items not readily identifiable or ob tainable. Over 85,000 references are now in the theoretical, and literature review program covering a set of properties of great importance to science and files. technology. Over the years, this program has grown Thus, the man who wants to use existing data, rather than make new measurements himself, faces steadily, producing bibliographies, data compila a long and costly task if he wants to assure himself tions and recommendations, experimental measure ments, and other output. The series of volumes for that he has found all the relevant results. More often which these remarks constitute a foreword is one of than not, a search for data stops after one or two results are found-or after the searcher decides he these many important products. These volumes are a monumental accomplishment in themselves, re has spent enough time looking. Now with the quiring for their production the combined knowledge appearance of these volumes, the scientist or engineer and skills of dozens of dedicated specialists. The who needs these kinds of data can consider himself very fortunate.