Cyfyngwch eich canlyniadau yn ôl:
- Pob un
- National Trust in Wales, 2 canlyniadau
- Trawsfynydd Nuclear Power Station (Wales), 1 canlyniadau
- Nature Conservancy Council (Great Britain), 1 canlyniadau
- Dinorwig Power Station (Wales), 1 canlyniadau
- Rio Tinto Zinc Corporation, 1 canlyniadau
- West Wales Naturalists' Trust, 1 canlyniadau
- National Trust in Wales -- Correspondence, 1 canlyniadau
- West Wales Naturalists' Trust -- Correspondence., 1 canlyniadau
- Scott, Peter, 1909-1989 -- Correspondence., 1 canlyniadau
- Pob un
- Housing development -- Wales, 1 canlyniadau
- Roads -- Wales, 1 canlyniadau
- Afforestation -- Wales, 1 canlyniadau
- Barrages -- Severn River (Wales and England), 1 canlyniadau
- Bridges -- Wales, 1 canlyniadau
- Historic buildings -- Conservation and restoration -- Wales, 1 canlyniadau
- Hydroelectric power plants -- Wales, 1 canlyniadau
- Industrial development projects -- Wales, 1 canlyniadau
- National parks and reserves -- Wales, 1 canlyniadau
- Nuclear power plants -- Wales, 1 canlyniadau