@inbook { kerres_potenzial, title = {Potenziale von Web 2.0 nutzen}, booktitle = {Handbuch E-Learning}, year = {2006}, publisher = {DWD-Verlag}, organization = {DWD-Verlag}, address = {M{\"u}nchen}, author = {Michael Kerres}, editor = {Hohenstein, A. and Karl Wilbers} } @inbook { petschenka_lerna, title = {Lernaufgaben beim E-Learning}, booktitle = {Handbuch E-Learning}, volume = {Kap. 4.19}, year = {2004}, publisher = {Wolters-Klouwer}, organization = {Wolters-Klouwer}, address = {K{\"o}ln}, author = {Petschenka, Anke and Nadine Ojstersek and Michael Kerres}, editor = {Hohenstein, A. and Karl Wilbers} }