Hensel, Sebastian Max Planck Institute for Mathematics, Max Planck Society;
http://bib.math.uni-bonn.de/downloads/bms/BMS-406.pdf (Any fulltext)
Hensel, S. (2011). Metric distortion of subgroups of mapping class groups. PhD Thesis, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn.