- C1, US Developments in Calculating Machines. An informal and unofficial survey by Hartree from notes made in the course of a visit to the USA, May-July 1945. Typescript, pp.17. Document is stamped Confidential and is marked on top: Given to L.J. Comrie by JRW [Womersley?];
- C2, Hartree, Experimental Arithmetic, typescript, pp. 7, c 1947;
- C3, Lecture given by Professor D.R. Hartree on April 15th 1947, 2 typescripts, pp. 3, pp. 8;
- C4, Hartree, Differential Analyser, Ministry of Supply Monograph, January 1949, pp. 75 + diagrams.