@article{SPS_2001__35__1_0,
     author = {Nagasawa, Masao and Tanaka, Hiroshi},
     title = {The principle of variation for relativistic quantum particles},
     journal = {S\'eminaire de probabilit\'es de Strasbourg},
     pages = {1--27},
     publisher = {Springer - Lecture Notes in Mathematics},
     volume = {35},
     year = {2001},
     mrnumber = {1837274},
     zbl = {0981.60100},
     language = {en},
     url = {http://www.numdam.org/item/SPS_2001__35__1_0/}
}