*{{cite MacTutorweb History|title=Arthur ofGeoffrey MathematicsWalker |first1=J J |last1=O'Connor article|first2=E [F |last2=Robertson|url=http://www-history.mcs.st-andrews.ac.uk/Biographies/Walker_Arthur.html http://www-history.mcs.st-andrews.ac.uk/Biographies/Walker_Arthur.html]|publisher=School of Mathematics and Statistics; University of St Andrews, Scotland |accessdate=17 January 2015}}