- NLW MSS 23612-56.
- Is-fonds
- 1785-[c. 1955].
Rhan oPapurau O. Llew Owain
Manuscripts and papers, 1785-[c. 1955], from the library of O. Llew Owain, including correspondence, eisteddfod and other essays, and manuscripts of Caernarfonshire interest; also included are letters to John Thomas (Eifionydd) and to Beriah Gwynfe Evans, mostly relating to 'Gorsedd Beirdd Ynys Prydain'