| RefNo | Title | Date |
| NLB/30/186 | Copy letter from Francis Darwin, to Professor Magnus Gustaf Retzius, [Fellow of the Royal Society] | 8 February 1905 |
| NLB/38/382 | Copy letter from Robert William Frederick Harrison, to Professor Magnus Gustaf Retzius, Foreign Member of the Royal Society | 24 July 1908 |
| NLB/37/217 | Copy letter from Robert William Frederick Harrison to Professor Sidney [Harris Cox] Martin FRS, Chairman of the Physiology Sectional Committee | 17 February 1908 |
| NLB/38/92 | Copy letter from Archibald Geikie, to Professor [Magnus Gustaf] Retzius, [Foreign Member of the Royal Society] | 15 June 1908 |
| MC/23/387 | Letter from [Magnus] Gustaf Retzius, Zoological Station, Fiskebäckskil, Sweden, to Doctor [Robert] Harrison, [Royal Society] | 28 July 1908 |
| NLB/37/781 | Copy letter from Robert William Frederick Harrison to Professor [Magnus Gustaf] Retzius, Foreign Member of the Royal Society | 15 May 1908 |
| NLB/38/433 | Copy letter from Robert William Frederick Harrison, to Professor Magnus Gustaf Retzius, Foreign Member of the Royal Society | 4 August 1908 |
| NLB/57/144 | Copy letter from Robert William Frederick Harrison, Assistant Secretary of the Royal Society; to Sir Edward Sharpey Schafer, FRS | 29 July 1919 |
| EC/1907/21 | Retzius, Magnus Gustaf: certificate of election to the Royal Society | |
| NLB/57 | New Letter Book volume 57, copy letters sent from Royal Society administration | 27 June 1919-27 February 1920 |
| MC/24/122 | Letter from Gustaf Retzius, Stockholm, to Dr [Robert] Harrison, [Royal Society] | 12 January 1909 |
| MC/23/388 | Letter from [Magnus] Gustaf Retzius, Drottninggatan, Stockholm, to Mr [Robert] Harrison, [Royal Society] | 15 October 1908 |
| MC/23/386 | Letter from [Magnus] Gustaf Retzius, Stockholm, to Mr [Robert] Harrison, [Royal Society] | 22 May 1908 |
| MC/23/384 | Letter from [Magnus] Gustaf Retzius, Stockholm, to Professor [John Rose] Bradford, [Royal Society] | 19 April 1908 |
| MC/23/385 | Letter from [Magnus] Gustaf Retzius, Hotel Cecil, Strand, WC, to Mr [Robert] Harrison, [Royal Society] | 15 May 1908 |
| NLB/37/286 | Copy letter from John Rose Bradford to Professor Gustaf Retzius, Foreign Member of the Royal Society | 25 February 1908 |
| MC/23/383 | Letter from [Magnus] Gustaf Retzius, Drottninggatan, Stockholm, to Professor [John Rose] Bradford, [Royal Society] | 22 March 1908 |
| NLB/37/644 | Copy letter from Robert William Frederick Harrison to Professor G [Gustav Magnus] Retzius, Foreign Member of the Royal Society | 24 April 1908 |
| NLB/38/666 | Copy letter from Robert William Frederick Harrison, to Professor Magnus Gustaf Retzius, Foreign Member of the Royal Society | 20 October 1908 |
| NLB/39/450 | Copy letter from Robert William Frederick Harrison to Professor [Magnus] G [Gustav] Retzius, Foreign Member of the Royal Society | 20 January 1909 |
| MC/17 | Volume 17 of miscellaneous correspondence regarding business matters, sent to the Royal Society | 1897-1899 |
| MC/22/348 | Letter from [Magnus] Gustaf Retzius, 110 Drottninggatan, Stockholm, to Lord Rayleigh, President of the Royal Society | 23 June 1907 |
| MC/22 | Volume 22 of miscellaneous correspondence regarding business matters, sent to the Royal Society | 1907 |
| MC/23/381 | Letter from Anna Hierta-Retzius, Drottninggatan, Stockholm, to Professor [John Rose] Bradford, [Royal Society] | 23 August 1908 |
| MC/23/382 | Letter from [Magnus] Gustaf Retzius, Drottninggatan, Stockholm, to Professor [John Rose] Bradford, [Royal Society] | 5 March 1908 |