[footnote 21] The Royal Society and the British Academy (2018) 'Harnessing Educational Research', London: The Royal Society and the British Academy, 51.
[troednodyn 21] Y Gymdeithas Frenhinol a’r Academi Brydeinig (2018) 'Harnessing Educational Research', Llundain: Y Gymdeithas Frenhinol a’r Academi Brydeinig, 51.