From: crstover@aol.com (CRStover)
Newsgroups: sci.math.research
Subject: Re: Obstruction theory
Date: 10 Nov 1995 17:08:48 -0500

> In his book ``The topology of fibre bundles'', N. Steenrod developed an
> obstruction theory for extension of cross-section based on primary
> obstruction.... 

This elementary obstruction theory generalizes to a spectral sequence that
has long been part of the folklore of homotopy theory. The definitive
reference would probably be section 7 of A. K. Bousfield, Homotopy
Spectral Sequences and  Obstructions, Israel Journal of Math., 66, 1989. 

Chris Stover
crstover@aol.com