Griffith John Williams y "Cymro Amryddawn" o Flaenau Ffestiniog /
Jones, Dafydd.
Cymdeithas y Fainc Sglodion.
Ffestiniog : Cymdeithas y Fainc Sglodion,
2009.
Williams, G. J. (Griffith John), 1854-1933.
Geologists
Antiquarians