Maintenance work on the ZORA database servers is scheduled for Thursday 25th July 2019 from 19:00-20:00. During this period ZORA and JDB will not be available. Thank you for your understanding.
Straumann, Ralph K; Purves, Ross S (2008). Delineation of valleys and valley floors. In: Cova, T J; et al. Geographic Information Science. Berlin, Heidelberg: Springer Verlag, 320-336.