were published as Aspects of Prehistory by the University of California Press in 1970. He published a classification system of five "lithic modes" or types of stone tools in 1969, which is still in use today. In 1970, Clark retired as editor of the Proceedings. In 1972, Clark spent time at Uppsala University as a visiting professor. That same year, Clark returned to the subject of Star Carr to publish a book for undergraduate students, Star Carr: A Case Study in Bioarchaeology. Towards the end of his career, Clark was given a range of awards in recognition of his research output: the Smithsonian Institution's Hodgkins Medal in 1967, the Wenner-Gren Foundation's Viking Fund Medal in 1971, Commander of the Order of the British Empire in 1971, the University of Pennsylvania's Lucy Wharton old Medal in 1974, the Society of Antiquaries' Gold Medal in 1978, and the Asiatic Society's Chandra Medal in 1979. Two festschrift's were also produced in his honour: a 1971 volume of the Proceedings was devoted to him, while in 1976, Gale de Giberne Sieveking, Ian H. Longworth, and Kenneth E. Wilson produced the edited volume Problems in Economic and Social Archaeology, which again was dedicated to Clark. Later life: 1973–95 Clark retired as Disney Professor in 1974. From 1973 until 1980 he served as the Master of Peterhouse, in what became some of the happiest years of his life. In 1975, he revised may of his ideas on Mesolithic Northern Europe for The Earlier Stone Age Settlement of Scandinavia. The book was not well received, with many archaeologists working on Scandinavian material deeming it outdated. In 1976, he made a coast-to-coast trip across Canada, and that year chaired the first meeting of the Science-based Archaeological Committee, which had been established by the Science Research Council in order to distribute funds to archaeological projects. In 1977, he published a third edition of World Prehistory, now retitled World Prehistory in New Perspective. From 1974 to 1978, he chaired the British Academy's Section Ten, which was devoted to archaeology and anthropology. In 1978 he travelled to New Delhi to attend the Wheeler Memorial Lecture of the Archaeological Survey of India at the invitation of B. K. Thapar. In 1980, Clark's short book, Mesolithic Prelude was published, based on his 1979 Munro Lecture. In 1982, Methuen then published Clark's The Identity of Man as Seen by an Archaeologist, in which he