Here's a reading list I put together over the years on the subject.
1. Costas, J.P., "Synchronous Communications," Proceedings of the IRE, Dec 1956, pp. 1713-1718.
2. Correspondence, "The Synchrodyne," Electronic Engineering, July 1947, pages 238 and xvi.
3. Crosby, Murray G., "Exalted-Carrier Amplitude- and Phase-Modulation Reception," Proceedings of the IRE, Sep 1945, pp. 581-591.
4. Herbert, J.W., "A Homodyne Receiver," Wireless World, Sep 1973, pp. 416-419.
5. Hershberger, Dave, "Build A Synchronous Detector for AM Radio," Popular Electronics, April 1982, pp. 61-71.
6. Hood, J.L. Linsley, "Synchrodyne A.M. Receiver," Wireless World, Jan 1986, pp. 51-53, Feb 1986, pp. 53-56, Mar 1986, pp. 58-61.
7. Johnson, Steve, "Synchronous Detection of AM Signals: What is it and how does it work?", QEX, Sep 1992.
8. Jones, Howard E., "Dual Output Synchronous Detector Utilizing Transistorized Differential Amplifiers," US Patent #3,241,078, Mar 15, 1966.
9. Macario, R.C.V., "How Important Is Detection?," Wireless World, Apr 1963, pp. 52-57.
10. Nagle, William, “The Synchronous Detection Process,” 73 Magazine, Sep 1967, pp. 6-11.
11. Nauta, H.C. and E.H. Nordholt, "A Novel High-Dynamic-Range PLL System for Synchronous Detection in AM Receivers," IEEE Transactions on Consumer Electronics, Vol. CE-31, No. 3, Aug 1985, pp. 447-455.
12. Novinger, Walter, "Johnson's Synchronous Detector Kit," Electric Radio, Oct 1994 (Issue 66), pp. 18,36-7.
13. Pik, J.P., "High Fidelity (Snychrodyne) AM Broadcast Tuner," Proceedings of the IREE Australia, Sep 1975, pp. 300-309.
14. Prather, Scott, "A Unique Approach to AM Synchronous Detection," Communications Quarterly, Fall 1994. FAR Circuits has a $5.25 board,
www.cl.ais.net/farcir/. Article available at
http://swordmaking.webjump.com/radio/15. Priebe, H.F, Jr., “Auto-Product Detection of Double-Sideband,” Ham Radio, Mar 1980, pp. 58-61.
16, Staples, John, "Synchronous Detectors," Electric Radio, Oct 1991, pp. 10-13.
17. Staples, John, "A Practical Synchronous Detector," Electric Radio, February 1992 (Issue 34), pp. 12-15.
18. Tucker, D.G., "The Design of a Synchrodyne Receiver, Part I - Design Principles," Electronic Engineering, August 1947, pp. 241-245.
19. Tucker, D.G., "The Design of a Synchrodyne Receiver, Part II - Some Suitable Designs," Electronic Engineering, Sep 1947 pp. 276-77.
20. Tucker, D.G., "The History of the Homodyne and Synchrodyne," Journal of the British Institution of Radio Engineers, Apr 1954, pp. 143-154.
21. Tucker, D.G., "The Synchrodyne, A New Type of Radio Receiver for AM Signals," Electronic Engineering, March 1947, pages 75-76.
22. Tucker, D.G. and J. Garlick, "The Synchrodyne: Refinements and Extensions," Electronic Engineering, Feb 1948, pages 49-54.
23. Tucker, D.G. and R.A. Seymour, "The Synchrodyne As a Precision Demodulator," The Wireless Engineer, Aug/Sep 1950, pp. 227-237.
24. Vermasvuori, Jukka, "A Synchronous Detector for AM Transmissions," QST, July 1993, pp. 28-33.
25. Webb, John K., “A Synchronous Detection Adapter for Communications Receivers,” CQ, June 1957, pp. 30-33, 117.
26. Young, Paul H., “Electronic Communication Techniques, Fourth Edition.”