The above article (DOI: 10.1002/spe.1105) was published in print in Volume 42, Issue 8 (August 2012), for which errors in the arrangement of the affiliation links have subsequently been identified. This article has been corrected in the online version of the issue.

The affiliation links have been corrected as follows:Vijay Nagarajan1, Dennis Jeffrey2, Rajiv Gupta3 and Neelam Gupta1School of Informatics, University of Edinburgh, Edinburgh, EH8 9AB, UK2Google Inc., 1600 Amphitheatre Parkway, Mountain View, CA 94043, USA3CSE Department, University of California at Riverside, Riverside, CA 92521, USA