In Thomson's letter to Ledermann, dated 19 Jun 1939, he apologises for not replying to an earlier letter of Ledermann's and informs him that he will be happy to send him any of the letters he has written regarding his work from the last year, asking him to specify the subjects he is interested in.

In his reply, dated 24 Jun 1939, Ledermann tells Thomson that he would like to look at the problem of maximising and minimizing the specifics, and that he has not managed to progress much with W G Madow's paper on multivariate statistical analysis.