The prospect of extending the marketing mix first took hold at the inaugural AMA Conference dedicated to Services Marketing in the early 1980s, and built on earlier theoretical works pointing to many important limitations of the 4 Ps model. Taken collectively, the papers presented at that conference indicate that service marketers were thinking about a revision to the general marketing mix based on an understanding that services were fundamentally different from products, and therefore required different tools and strategies. In 1981, Booms and Bitner proposed a model of 7 Ps, comprising the original 4 Ps extended by process, people and physical evidence, as being more applicable for services marketing.