"Courses Ongoing--Introduction to Unix and Hands-On Unix Networking; sponsored by the American Institute. Call in N.Y. (212) 826-1260, or outside N.Y. (800) 345-8016.May 31-June 4--Sybase User Meeting & Training Conference; sponsored by Sybase, Inc.; San Jose Convention Center, California. Call in the U.S. and Canada (800) 767-2336, or outside (508) 470-0526.June 4--Government Securities: New Legislative and Regulatory Developments; sponsored by the Public Securities Association; Vista Inter