https://link.springer.com/article/10.1007/s00422-017-0722-1
An earlier draft (by now substantially revised) is still available online under a different title:
http://pub.math.leidenuniv.nl/~doelmana/HP_PUB/vdSD_neutral.pdf
http://www.math.leidenuniv.nl/~doelman/HP_PUB/vdSD_neutral.pdf
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.701.7705&rep=rep1&type=pdf
https://esc.fnwi.uva.nl/thesis/centraal/files/f2070098628.pdf
http://dare.uva.nl/document/342022
http://dare.uva.nl/cgi/arno/show.cgi?fid=342022
(with my cousin and uncle in our home-made iceboat)
(those few that fit in my document scanner)
footnote text comes here.↩