Volume 90, Issue 2, September 1969

## The second homotopy group of spun 2-spheres in 4-space

Pages 199-204 by James J. Andrews, Samuel J. Lomonaco

## Rational homotopy theory

Pages 205-295 by Daniel Quillen

## Wall’s surgery obstruction groups for $G\times Z$

Pages 296-334 by Julius L. Shaneson

## On the zeta function of a hypersurface. IV. A deformation theory for singular hypersurfaces

Pages 335-352 by Bernard M. Dwork

## A uniqueness theorem for the Neumann problem

Pages 353-360 by William J. Sweeney

## A countable infinity of $\Pi_1$ factors

Pages 361-371 by Dusa McDuff

## Uncountably many $\Pi_1$ factors

Pages 372-377 by Dusa McDuff