{{Ref|Ashliman 2010|x}}
{{Ref|Bacon 1914|x}}
{{Ref|Farbregd 1972|x}}
{{Ref|Garnet 1912|x}}
{{Ref|Goodwin 1948|x}}
{{Ref|Halpin 2008|x}}{{Ref|Hoernig 2005|x}}
{{Ref|Ingram 1912|x}}
{{Ref|Killings 1996|x}}
{{Ref|King 2007|x}}
{{Ref|Junkmanns 2013|x}}{{Ref|Lansac 2008|x}}{{Ref|Lanting 1999|x}}{{Ref|Owen & Dalland 1999|x}}{{Ref|Paulsen 1999|x}}{{Ref|Roesdahl & Wilson 1992|x}}{{Ref|de Stoute 2008|x}}{{Ref|Szabo 1985|x}}
{{Ref|Taylor 1837|x}}
{{Ref| Westphal 2006|x}}
<HarvardReferences />