Henry Oldenburg wrote to Leeuwenhoek in response to his letter of 1675-01-22
Date:
February 19, 1675
At the bottom of Leeuwenhoek's Letter No. 15 [9] of 1675-01-22, Oldenburg wrote:
Answ. Febr. 19.167⅘. Kept no Copy.
Oldenburg wrote that letter when it was March 1 New Style in Holland.
Document:
Recorded in both Alle de Brieven / Collected Letters vol. I, p. 229 and The Correspondence of Henry Oldenburg, vol. 11, p. 201