Dear All, The forthcoming paper of Maarten Bullynck, Edgar Daylight, and Liesbeth De Mol is available from my website: http://www.dijkstrascry.com/Bullynck2015draft The link points to the peer-reviewed and accepted version of our paper, which will appear in the Communications of the ACM in March 2015 (give or take a month), but which has yet to be technically edited by a native English speaker. best wishes, Edgar.