Cyfyngwch eich canlyniadau yn ôl:
- Pob un
- Slate industry -- Wales, 6 canlyniadau
- Environmental protection -- Great Britain, 1 canlyniadau
- Land use -- Great Britain, 1 canlyniadau
- Coal mines and mining -- Great Britain, 1 canlyniadau
- Forests and forestry -- Great Britain, 1 canlyniadau
- Quarries and quarrying -- Wales, 1 canlyniadau
- Land value taxation, 1 canlyniadau