@incollection{Mohren2004, author = {Mohren, Henning}, title = {Zertifikate an der FernUniversit{\"a}t}, series = {Jahrbuch der FernUniversit{\"a}t in Hagen}, booktitle = {Jahrbuch der FernUniversit{\"a}t in Hagen}, address = {Hagen}, year = {2004}, language = {de} }