{{Ref|Book=Bailey 1980}}
{{Ref|Book=Bersu & Wilson 1966}}
{{Ref|Book=Bjorn 1940}}
{{Ref|Book=Cameron 2000}}
{{Ref|Book=Cameron 2003}}
{{Ref|Book=Okasha 1992}}
{{Ref|Book=Parker Library}}
{{Ref|Book=Paterson 2014}}
{{Ref|Book=Vince 1991}}
{{Ref|Book=Wilson 1964}}
{{Ref|Book=Wilson 1965}}
{{Ref|Book=Wilson 1985}}