TRS-80 Model 4 (English Wikipedia)

"LSI Delivers". 80 Micro (Advert). May 1987. p. 10. Retrieved October 22, 2019.
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Dalton, David (September 1985). "The Enhancer". 80 Micro. CW Communications. p. 33. Retrieved November 5, 2019.
Snyder, E. Cameron (August 1985). "The Great Divide". 80 Micro. CW Communications. p. 63. Retrieved November 5, 2019.
Harrell, John B. (March 1985). "CP/M 2.2 Revisited". 80 Micro. CW Communications. p. 35. Retrieved July 9, 2020.
Harrell, John B. (August 1985). "A Window on the CP/M World". 80 Micro. CW Communications. p. 36.
Ludwig, Gary A. (October 1985). "Concurrent Events with DoubleDuty". 80 Micro. CW Communications. p. 36. Retrieved July 9, 2020.
Davis-Wright, Ryan (November 1985). "PRO-NTO: TRSDOS 6.x's Sidekick". 80 Micro. CW Communications. p. 29. Retrieved July 9, 2020.
Potter, William H. (August 1987). "4 In the Fast Lane". 80 Micro. CW Communications. p. 38. Retrieved July 9, 2020.
Ahl, David H. (December 1984). "Top 12 Computers of 1984". Creative Computing. 10 (12): 14, 16. ISSN 0097-8140. Retrieved April 27, 2023 – via Internet Archive.

atarimagazines.com

Juge, Ed (October 1985). "News for the top: what's really going on at Tandy". Creative Computing. p. 108. Retrieved 14 October 2016.

Bartimo, Jim (March 11, 1985). "Tandy Revamps Product Line". InfoWorld. Vol. 7, no. 10. pp. 28–29. Retrieved January 21, 2015.
Daneliuk, Tim (1983-11-21). "Review: Radio Shack TRS-80 Model 4P". InfoWorld. Vol. 5, no. 47. pp. 82–83. Retrieved 2020-04-13.
Tooley, Michael (1988). Servicing Personal Computers. Heinemann Professional Publishing. p. 146, table 4.3. ISBN 978-1-4831-0103-3.

"1984 Radio Shack Computer Catalog RSC-10 page 18". radioshackcatalogs dot com. Tandy/Radio Shack. 1984. Retrieved November 25, 2022.
"1990 Radio Shack Computer Catalog RSC-21 page 34 (effective thru fall 1991)". radioshackcatalogs dot com. Tandy/Radio Shack. 1990. Retrieved November 25, 2022.
"1985 Radio Shack Computer Catalog RSC-12 page 28". radioshackcatalogs dot com. Tandy/Radio Shack. 1985. Retrieved November 25, 2022.
"Radio Shack Computer Catalog CCF-836, page 9". Radio Shack Catalogs dot com. Tandy/RadioShack. 1983. Retrieved November 25, 2022.
"1985 Radio Shack Computer Catalog pg. 28". Radio Shack Catalogs. Avnet Electronic Components. 1985. Retrieved October 25, 2016.
"First appearance of DDuty in RS Computer Catalog RSC-12 page 27, 1985". Radio Shack Catalogs dot com. Tandy/Radio Shack. Retrieved December 2, 2022.
"1990 Radio Shack Computer Catalog RSC-21 page 34 (effective thru fall 1991)". radioshackcatalogs dot com. Tandy/Radio Shack. 1990. Retrieved November 26, 2022.

Soltoff, Roy (Winter 1987). "LDOS 5.3 Model 4 Hardware Interface Kit" (PDF). The Misosys Quarterly. Vol. I, no. iii. Misosys, Inc. p. 6. Retrieved November 6, 2019 – via tim-mann dot org.
Soltoff, Roy. "DoubleDuty 2.6.0 Released" (PDF). The Misosys Quarterly. Misosys, Inc. Retrieved July 17, 2020 – via www.tim-mann dot org.
Sherman, Lynn R. "CTL255/FLT" (PDF). The Misosys Quarterly. Roy Soltoff, Misosys, Inc. p. 40. Retrieved July 17, 2020 – via www.tim-mann dot org.
Tam, Tsun (Spring 1990). "Upgrade Your 4P with External Floppy Drives" (PDF). The Misosys Quarterly. Vol. IV, no. iii. 80 Micro (reprinted by Roy Soltoff/Misosys Inc.). p. 27. Retrieved May 14, 2019 – via tim-mann dot org.
Soltoff, Roy (Fall 1986). "LDOS 5.3.0 Upgrade Kit" (PDF). Misosys Quarterly. Vol. I, no. ii. Misosys, Inc. p. 13. Retrieved February 18, 2020 – via tim-mann dot org.

Goldklang, Ira (March 4, 2009). "TRS-80 Computers: TRS-80 Model 4". Ira Goldklang's TRS-80 Revived Site. Retrieved 2019-05-19.
Goldklang, Ira. "TRS-80 – CP/M". Ira Goldklang's TRS-80 Revived Site. Retrieved 2019-05-19.