| "Unanswered Call Diverter", IBM Technical Disclosure Bulletin, vol. 25, No. 7A, Dec. 1982, pp. 3480-3481. |
| M. Hills & S. Kano, "Programming Electronic Switching Systems-Real-Time Aspects and Their Language Implications", pp. 9 & 21-47, IEEE Telecommunications Series 3 (Peter Peregrinus Ltd. 1976). |
| "Rolm Centralized Attendant Service", Rolm Corp. (1979). |
| "AIS Automatic Intercept Service Versatile Efficient Information Service", Fujitsu Limited (date stamped 1972). |
| "Data Set 407 Interface Specification", AT&T (Jun. 1975). |
| "ROLMphone User guide", pp. 2-4, 17, 24, 83, and 86 (Rolm Jul. 1985). |
| L. Goeller, Jr. & J. Goldstone, "The ABCs of the PBX", Datamation pp. 9-13 (Apr. 1983). |
| T. Kopec & P. Lind, "Electronic Business Telephone", GTE Automatic Electric Journal pp. 34-40 (Mar. 1980). |
| K. Tapper & P. Thatte, "GTD-1000 Digital PABX CAS Main/ACD", GTE Automatic Electric Journal, pp. 182-193 (Nov. 1980). |
| R. Kaloian, "What if you cut over a new telecom system . . . and nobody used it?", Communication Age, pp. 46-47 and 50 (Sep. 1986). |
| Aspen Voice Message Systems Data Sheets, Octel Communications Corp., 1985. |
| ROLM Phonemail Integration for Meridian SL-1 PBX Systems, Programming Announcement, IBM Corporation, (Sep. 8, 1987). |
| Voice Messaging Integrated with PBX and Centrex, Octel Communications Corporation, (Apr. 1988). |
| AUDIX: Audio Information Exchange, AT&T Information Systems. |
| Specifications for CINDI II VOICE MA053550380 IL, Genesis Electronics Corporation, (1987). |