Here is a reasonably current subset of available articles.

Widely available:

Unix Review, July 1992, Cross Thoughts Column
Gave a description of Wcl, and some code samples.

Unix Review, December 1992, Cross Thoughts Column
Griped about the Motif form widget, then presented the Table widget from
Wcl as a solution to most of the problems.

The X Resource, Issue 2 (or maybe 3) Spring 1992.  I don't have
a copy handy, so I can't be specific.

Not so widely available:

David E. Smyth.  Widget Creation Library, Motif Resource Interpreter,
Athena Resource Interpreter: An Easier Way to Develop Applications
using Motif and Athena Widgets, in JPL SFOC FIST Quarterly Report,
August 1990.

David E. Smyth.  Wcl-Widget Creation Library, Mri-Motif Resource
Interpreter, Ari-Athena Resource Interpreter: An Easier Way to
Develop Applications using Motif and Athena Widgets, The European X
Window System User Group Autumn Conference 1990 Proceedings.

David E. Smyth.  Wcl-Widget Creation Library, A Thin Veneer over Xrm,
The 5th Annual X Technical Conference 1991 Proceedings.

David E. Smyth. Wcl-The Widget Creation Library, A Better Motif API,
Motif 91, the International Motif User s Group Conference 1991
Proceedings.

Steve Wright, David Smyth, Rashmi Dalany, Kathy Surdevant.  Space
Flight I Operations Center Telemetry Delivery System Software
Specification Document STDS0007-00-01, JPL, 1990.