Sommer, R.; Fölster, H.; Vielhauer, K.; Maklouf Carvalho, E.J. and P. L. G. Vlek; 2003. Deep soil water dynamics and depletion by secondary vegetation in the eastern Amazon. Soil Sci. Soc. Am. J., 67: 1672-1686.

Sommer, R.; Sa, T. D. de A.; Vielhauer, K.; de Araujo, A. C.; Fölster, H. and P.L.G. Vlek; 2002. Transpiration and canopy conductance of secondary vegetation in the Eastern Amazon. Agric. Forest Meteorol., 112: 103-121.

Sommer, R.; Sá, T. D. de A.; Vielhauer, K.; Fölster, H.; and P.L.G. Vlek; 2001. Water and nutrient balance under slash-and-burn agriculture in the Eastern Amazon, Brazil - The role of a deep rooting fallow vegetation. In: Horst W.J. et al. (eds.). Plant Nutrition. Food security an sustainability of agro-ecosystems through basic and applied research. Kluwer Academic Publisher. pp. 1014-1015.

Sommer, R.; Denich, M. and P.L.G. Vlek; 2000: Carbon storage and root penetration in deep soils under small-farmer land-use systems in the Eastern Amazon region, Brazil. Plant Soil, 219: 231-240.

Sommer, R.; White, J.W.; Wall, P.C. and K.D. Sayre; 2003. Model-based assessment of maize cropping under conventional and zero-tillage in highland Mexico – preliminary results. Poster presented at the 2003 Annual Meetings of the ASA-CSSA-SSSA, Denver, Colorado, USA, November 2–6. Annual Meetings Abstract CD.