@article{RSMUP_1976__56__139_0,
     author = {Battaia, Luciano},
     title = {A principle involving the variation of the metric tensor in a stationary space-time of general relativity},
     journal = {Rendiconti del Seminario Matematico della Universit\`a di Padova},
     pages = {139--145},
     publisher = {Seminario Matematico of the University of Padua},
     volume = {56},
     year = {1976},
     mrnumber = {479288},
     zbl = {0381.53021},
     language = {en},
     url = {http://archive.numdam.org/item/RSMUP_1976__56__139_0/}
}