@book{DerMartius11, title = {{T}he {P}layful {M}achine - {T}heoretical Foundation and Practical Realization of Self-Organizing Robots}, author = {Der, Ralf and Martius, Georg}, publisher = {Springer}, address = {Berlin Heidelberg}, year = {2012}, doi = {}, url = {http://playfulmachines.com} }