"In the fall of 1965, two large projects were set in motion to develop contemporary thesauri in the fields of engineering and science. One was originated by Engineers Joint Council to revise the first edition of its Thesaurus of Engineering Terms (1964); the other, by the Department of Defense, under the sponsorship of the Office of Naval Research and known as Project LEX, which had as its mission the development of the first Department of Defense technical thesaurus. The large number of related and overlapping interests of these two separate projects soon motivated a merging of the efforts. The need for commonality in information systems and in reduction of communication barriers was also a driving force, as was the economic advantage of pooling resources, especially available technical personnel. Preparation and presentation agreements were readily reached and a joint working arrangement made for the two projects to join forces in one operation. Hence, this single work, Thesaurus of Engineering and Scientific Terms, which is also available on magnetic tape, is a thesaurus for both Engineers Joint Council and the Department of Defense."