*Editors*: D.G. Bourgin (Houston), B. Jóhnson (Nashville), A. Lelek (Houston), J.S. Mac Nerney (Houston), J.W. Neuberger (Emory), B.H. Neumann (Australian National University), J. Schmidt (Houston)
*Managing Editor*: G.G. Johnson (Houston)
*Associate Managing Editors*: J. Hausen (Houston), J.A. Johnson (Houston)

Houston Journal of Mathematics

*Contents*

**E. Z. Andalafte, J. E. Valentine, S. G. Wayment
**

Triangle Median Properties Which Characterize Banach Spaces, pp. 307-312.

**David P. Bellamy
**

Homeomorphisms of Composants, pp. 313-318.

**Bang-Yen Chen
**

Extrinsic Spheres in Riemannian Manifolds, pp. 319-324.

**Harvey Friedman
**

On the Naturalness of Definable Operations, pp. 325-330.

**J. Grispolakis, E. D. Tymchatyn
**

Confluent Images of Rational Continua, pp.
331-337.

**David Handel
**

Obstructions to 3-Regular Embeddings, pp.
339-343.

**P. Krupski
**

Continua Which Are Homogeneous With Respect to Continuity, pp. 345-356.

**Jimmie D. Lawson
**

The Duality of Continuous Posets, pp. 357-386.

**Stephen Pierce
**

Divisibility Questions in the General Linear Group, pp. 387-394.

**Eric E. Robinson
**

Inverse Systems for Light-Open Mappings Onto Polyhedra, pp. 395-406.

**J. Wolfgang Smith
**

Compactly Generated Submersions, pp.
407-417.

**William W. Smith
**

Erratum to ``Invertible Ideals and Overrings'',
p. 419.

**R. C. Thompson
**

Invariant Factors of Complementary Minors of Integral Matrices, pp. 421-426.

**Constantine Tsinakis
**

Brouwerian Semilattices Determined by Their Endomorphism Semigroups, pp. 427-436.

**Mary H. Upham
**

Two Remarks on Duality, pp.
437-443.

**Nick Williams
**

Universe Developable Spaces, pp. 445-450.