@article{SEMR_2012_9_a12,
     author = {A. D. Mednykh},
     title = {Brahmagupta formula for cyclic quadrilaterals in the hyperbolic plane},
     journal = {Sibirskie \`elektronnye matemati\v{c}eskie izvesti\^a},
     pages = {247--255},
     publisher = {mathdoc},
     volume = {9},
     year = {2012},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SEMR_2012_9_a12/}
}