This volume concerns spectra with enriched multiplicative structure. It is truism that interesting cohomology theories are represented by ring spectra, the product on the spectrum giving rise to the cup products in the theory. Ordinary cohomology with mod p coefficients has Steenrod operations as well as cup products. These correspond to an enriched multiplicative structure on the Eilenberg-MacLane spectrum HZ . Atiyah has shown that the Adams operations in KU-theory are related similar structure on its representing spectrum and torn Dieck and Quillen have considered Steenrod operations in cobordism coming from similar structure on Thorn spectra. Kahn, Toda, Milgram, and others have exploited the same kind of structure
the sphere spectrum to construct and study homotopy operations, and Nishida's proof of the nilpotency of the stable stems is also based on this structure on the sphere spectrum.