Klaus published more than 600 original papers, mostly in the field of clinical chemistry and urological malignancies. To further appreciate this number, consider that he never had a secretary or an army of coworkers to help him, and he was never the senior author just because he was the lab Director. Before the Berlin Wall came down, he already was sending out manuscripts illegally via friends, taking a serious personal risk. The intensity of his work during his research career is outstanding and incomparable.