Genre
- Congresses 20 canlyniadau
- Guidebooks 14 canlyniadau
- Observations 14 canlyniadau
- Maps 7 canlyniadau
- Handbooks, manuals, etc 4 canlyniadau
- Surveys 3 canlyniadau
- Case studies 2 canlyniadau
- Bibliography 1 canlyniadau
- Charts, diagrams, etc 1 canlyniadau
- Classification 1 canlyniadau
- Pictorial works 1 canlyniadau
- Remote-sensing images 1 canlyniadau