Reference

A. Tsunekawa, T. Y. Ito, M. Shinoda, M. Nemoto, T. Suhama, H. Ju, H. Shimizu (2005): Methodology for Assessment of desertification based on Vegetation Degradation Using Net Primary Productivity (NPP) as a Key Indicator. – Phyton, Annales Rei Botanicae, Horn – 45_4: 185 - 192.