@unpublished{Shaw2011,
author = {Jonathan Shaw},
title = {FORTAX: UK tax and benefit system documentation},
year = {2011},
month = {May},
doi = {10.1920/wp.ifs.2011.1108},
issn = {1742-0415},
url = {http://www.ifs.org.uk/wps/wp1108.pdf},
}