--- ray/doc/ray.1	2018/06/26 14:42:18	1.35
+++ ray/doc/ray.1	2018/10/08 20:04:09	1.36
@@ -1,4 +1,4 @@
-.\" RCSid "$Id: ray.1,v 1.35 2018/06/26 14:42:18 greg Exp $"
+.\" RCSid "$Id: ray.1,v 1.36 2018/10/08 20:04:09 greg Exp $"
 .\" Print using the -ms macro package
 .DA 07/10/2016
 .LP
@@ -1593,6 +1593,12 @@ the Ecole Polytechnique Federale de Lausanne (EPFL Uni
 in Lausanne, Switzerland.
 .NH 1
 References
+.LP
+Wang, Taoning, Gregory Ward, Eleanor Lee,
+``Efficient modeling of optically-complex, non-coplanar
+exterior shading: Validation of matrix algebraic methods,''
+.I "Energy & Buildings",
+vol. 174, pp. 464-83, Sept. 2018.
 .LP
 Lee, Eleanor S., David Geisler-Moroder, Gregory Ward,
 ``Modeling the direct sun component in buildings using matrix