1. Relativity and Modern Physics;Birkhoff,1923
2. On the general spherically symmetric solutions of Einstein's gravitational equations in vacuo;Jebsen;Gen. Relativ. Gravit.,2005
3. On the discovery of Birkhoff's theorem;Voje Johansen;Gen. Relativ. Gravit.,2006
4. Gravitation and Cosmology;Weinberg,1972