Kochen, Walter (Ed.) and Hans Steinhart (Ed.). L-Tryptophan. Current Prospects in Medicine and Drug Safety. Berlin, Boston: De Gruyter, 1994. Web. Retrieved 24 May. 2013, from http://www.degruyter.com/view/product/173705

Kochen, W. (Ed.) & Steinhart, H. (Ed.) (1994). L-Tryptophan. Current Prospects in Medicine and Drug Safety. Berlin, Boston: De Gruyter. Retrieved 24 May. 2013, from http://www.degruyter.com/view/product/173705

Kochen, Walter (Ed.) and Hans Steinhart (Ed.). 1994. L-Tryptophan. Current Prospects in Medicine and Drug Safety. Berlin, Boston: De Gruyter. Retrieved 24 May. 2013, from http://www.degruyter.com/view/product/173705