Robat Powell

• Helynt haf
• Adroddiad ar yr arolwg sgiliau siarad ymhlith dysgwyr Cymraeg 10-11 oed, 1981
• Arolwg siarad Cymraeg 1985
• Cyfres Lleisiau
• Cyfres Tonic 5
• Haearn Iaith
• Report on the survey of listening comprehension skills among 11 year-old pupils learning Welsh as a second language, 1980
• Survey of Welsh oracy, 1989, among first and second language pupils age 13+
• Survey of Welsh reading and writing, 1988, among first and second language pupils aged 13+
• Survey of writing among 10-11 year old first language Welsh pupils
• Welsh reading survey, 1984
• Welsh speaking survey, 1985