Asesiad cyflym o’r dystiolaeth: Ymagweddau a dulliau addysgu ail iaith effeithiol - Steve Morris (2018)
https://llyw.cymru/sites/default/files/statistics-and-research/2019-06/180607-effective-second-language-treaching-approaches-methods-cy.pdf (and URL for Exec Summary is https://llyw.cymru/sites/default/files/statistics-and-research/2019-06/180607-effective-second-language-treaching-approaches-methods-summary-cy.pdf) Both are also available in English.