akkar_bommer_2010: equation bugfixes
bindi_2011: add missing IPE import
bindi_2011: equation bugfixes
cauzzi_faccioli_2008: equation bugfixes
chiou_youngs_2008: equation bugfixes
edwards_fah_2013a: equation bugfixes
edwards_fah_2013f: equation bugfixes
zhao_2006: equation bugfixes
akkar_bommer_2010: pep8 fixes
bindi_2011: pep8 fixes
cauzzi_faccioli_2008: pep8 fixes
chiou_youngs_2008: pep8 fixes
edwards_fah_2013a: pep8 fixes
edwards_fah_2013f: pep8 fixes
zhao_2006: pep8 fixes
zhao_2006: more pep8 fixes
edwards_fah_2013a: more pep8 fixes
edwards_fah_2013f: more pep8 fixes
akkar_bommer_2010: pep8 fixes / remove prints
cauzzi_faccioli_2008: pep8 fixes/remove dead code