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…