Matthias Opel, Stephan Geprägs, Matthias Althammer, Thomas Brenninger, Rudolf Gross: Laser molecular beam epitaxy of ZnO thin films and heterostructures. IOP Publishing Ltd. Bristol BS1 6BE, England 2014Journal of Physics D-Applied Physics: 47. ISBN 0022-3727 http://dx.doi.org/10.1088/0022-3727/47/3/034002