10.3842/SIGMA.2008.063
10.3842/SIGMA.2011.050
10.3842/SIGMA.2011.108
10.3842/SIGMA.2012.001
10.3842/SIGMA.2012.077
10.3842/SIGMA.2013.012
10.3842/SIGMA.2013.042
10.3842/SIGMA.2014.068
10.3842/SIGMA.2014.084
10.3842/SIGMA.2014.099
10.3842/SIGMA.2015.015
10.3842/SIGMA.2016.071