@book{252420,
	author = {Kopff, A.},
	title = {The mathematical theory of relativity /},
	publisher = {Methuen & Co,},
	year = {1923.},
	address = {London :},
	note = {"A first draft of this book was published in 1921 as a mathmathical supplement to the French edition of Space, time and gravitation."--Pref.}
}