Gwyddoniaeth trwy brofiad.
Jones, Elfrys.
Llandysul : Gomer mewn cydweithrediad a Heinemann Educational Books,
1991.
Arg Saesneg gwreiddiol = Original English ed: London: Inner London Education Authority, 1988
Cyfieithydd = Translator: Elfrys Jones
Rhai manylion teitl o'r clawr = Some cover details from cover
Science
Human ecology