Forum of Mathematics, Sigma /
Volume
1 /
Tue Jan 01 00:00:00 GMT 2013,
e4
(13 pages)
© The Author(s) 2013. The online version of this article is published within an Open Access environment subject to the conditions of the Creative Commons Attribution licence <http://creativecommons.org/licenses/by/3.0/>.
DOI:
http://dx.doi.org/10.1017/fms.2013.3
(About DOI),
Published online: Thu Sep 12 00:00:00 BST 2013