@book {Hawkes_1989_1,
	title = {Principles of Electron Optics},
	volume = {Volume 1 {\textendash} Basic Geometrical Optics},
	year = {1989},
	publisher = {Academic Press},
	organization = {Academic Press},
	address = {London},
	isbn = {0-12-333351-2},
	author = {P. W. Hawkes and E. Kasper}
}