H.454-H.460: General correspondence with American scientists and others, 1964-1972.

H.461: Correspondence and papers regarding a visit to the USA by Abraham in May, 1973.

H.462-H.464: General correspondence with American scientists and others, 1975-1991.

H.465-H.469: Correspondence with colleagues at Harvard regarding visits, conferences, lectures, publications etc., 1978-1993.

H.470-H.471: Correspondence with colleagues at Lederle Laboratories, Pearl River, New York, 1959-1963.

H.472-H.476:Correspondence with colleagues at the Massachusetts Institute of Technology regarding research, visits, publications etc., 1973-1991.