by Breitenlohner, Peter, Maison, Dieter, Lavrelashvili, George
Published in Classical and quantum gravity (21.03.2004)

by Brandt, S., Font, J.A., Ibáñez, J.Ma, Massó, J., Seidel, E.
Published in Computer physics communications (2000)

by Brosseau, Christian
Published in Progress in quantum electronics (01.01.1997)

by Sawczuk, Michal
Published in General relativity and gravitation (01.05.1994)

by PATEL, L. K, KOPPAR, S. S
Published in Letters in mathematical physics (01.07.1989)