Since the work of Stasheff and Sugawara in the 1960s on recognition of loop space structures on $H$-spaces, the notion of higher homotopies has grown to be a fu

Operads are mathematical devices which describe algebraic structures of many varieties and in various categories. From their beginnings in the 1960s, they have

The main theme of this book is that the use of filtered spaces rather than just topological spaces allows the development of basic algebraic topology in terms o