Papers of D. J. Williams, Llanbedr, Merionethshire, 1773-1949, comprising notebooks and other papers belonging to John Jones ('Tudur Llwyd') and John Peter, 'Ioan Pedr', 1773-1850; miscellaneous business papers, 1846-1903; notes, essays, books, and poems by D. J. Williams, 1911-1949; manuscripts of translations (by others) of books into Welsh, 1942-1945; notes and materials on the history of Llanderfel and Ardudwy, 1935-1938; manuscript and sources for Cyfres Chwedl a Chân, [1930s]; letters to D. J. Williams concerning children's stories, 1933-1949, from various authors; general correspondence of D. J. Williams, 1909-1941; papers relating to the translation into Welsh of school books and Welsh publications, 1932-1949; and radio scripts, stories, plays and lectures, by D. J. Williams and others [20th century].

Ffeilliau'n cynnwys gohebiaeth trefnwyr y prosiect a gwahanol sefydliadau a chyrff, 1968-1977, gan gynnwys y pwyllgor llywio,1969-1975; Pwyllgor Addysg Morgannwg, 1968-1977; awdurdodau addysg lleol, 1968-1974; Prifysgol Cymru, 1968-1974; Cyd-Bwyllgor Addysg Cymru, 1969-1973; ysgolion a gymerodd ran yn y prosiect, 1969-1975; Urdd Gobaith Cymru, 1970-1973; cwmnïau teledu, 1968-1973; cynlluniau eraill, 1970-1973; rheolau sefydlog a phapurau cyffredinol, 1969-1975; adroddiadau ar ysgolion unigol,1970-1974; cylchlythyrau, adroddiadau a phapurau ymchwil, 1968-1975; a phapurau'n ymwneud â phrofion, 1973-1974. = Files containing correspondence of the project organisers and various organisations and bodies, 1968-1977, including the steering committee, 1969-1975; Glamorgan Education Committee, 1968-1977; local education authorities, 1968-1974; the University of Wales, 1968-1974; the Welsh Joint Education Committee, 1969-1973; the schools involved with the project, 1969-1975; Urdd Gobaith Cymru, 1970-1973; television companies, 1968-1973; other schemes, 1970-1973; standing orders and general papers, 1969-1975; reports on individual schools, 1970-1974; circulars, reports and research papers, 1968-1975; and papers relating to tests, 1973-1974.

Cofnodion Pwyllgor Datblygu Addysg Gymraeg, PDAG, 1985-1994, yn cynnwys cofnodion cyfarfodydd, gohebiaeth, adroddiadau a deunydd ymchwil, gyda phapurau sydd yn ymwneud gan fwyaf â'r sector addysg yng Nghymru (ysgolion, prifysgolion a cholegau, ac addysg i oedolion) ac â chyrff megis y Swyddfa Gymreig, Bwrdd yr Iaith Gymraeg, Cyngor Cwricwlwm Cymru, Cydbwyllgor Addysg Cymru, Rhieni dros addysg Gymraeg, ac amryw gynghorau sir yng Nghymru = Records of the Welsh Education Development Committee (Pwyllgor Datblygu Addysg Gymraeg, PDAG), 1985-1994, including minutes of meetings, correspondence, reports and research material, with papers mostly relating to the Welsh education sector (schools, universities and colleges, and adult learning) and to bodies such as the Welsh Office, the Welsh Language Board, Curriculum Council for Wales, the Welsh Joint Education Committee, Parents for Welsh medium education, and to various county councils in Wales.