[[ENEV 94]		Ted Enever:		Britain's Best Kept Secret Ultra Base at Bletchley Park Alan Sutton Publishing Ltd., Printed in Great Britain, 1994.
[[ERDSUR 96]		Erdős Pál, Surányi János:		Válogatott fejezetek a számelméletből (in Hungarian) (Selected chapters from the theory of numbers) Polygon, Szeged, 1996.
	[ESSI 96]		J. Essinger:	Computer Security within Financial Institutions Financial Times, Financial Publishing, 1996.