 What precisely are E infinity ring spaces and E infinity ring spectra? by J. P. May

Primary author PDF: math.uchicago.edu/~may/PAPERS/Final1.pdf

Geometry and Topology Monographs 16, pages 215–282. DOI: doi.org/10.2140/gtm.2009.16.215

Sections 2 and 5 fix the countably infinite inner-product universe, finite-subspace indexing and the strict indexed-spectrum model. The text uses the mathematical symbol E infinity in its title; the source-card spelling keeps a stable readable identifier.