@article{MR_1981_24_a18,
     author = {Shudao Xu - Biao Xuang},
     title = {H {E\ensuremath{\xi}\ensuremath{\acute\epsilon}\ensuremath{\lambda}\ensuremath{\iota}\ensuremath{\xi}\ensuremath{\eta}} \ensuremath{\tau}o\ensuremath{\upsilon} {A\ensuremath{\nu}\ensuremath{\alpha}\ensuremath{\lambda}\ensuremath{\upsilon}\ensuremath{\tau}\ensuremath{\iota}\ensuremath{\kappa}o\ensuremath{\acute\upsilon}} {\ensuremath{\Pi}\ensuremath{\rho}o\ensuremath{\gamma}\ensuremath{\rho}\ensuremath{\acute\alpha}\ensuremath{\mu}\ensuremath{\mu}\ensuremath{\alpha}\ensuremath{\tau}o\ensuremath{\varsigma}} \ensuremath{\tau}\ensuremath{\omega}\ensuremath{\nu} {M\ensuremath{\alpha}\ensuremath{\theta}\ensuremath{\eta}\ensuremath{\mu}\ensuremath{\alpha}\ensuremath{\tau}\ensuremath{\iota}\ensuremath{\kappa}\ensuremath{\acute\omega}\ensuremath{\nu}} {\ensuremath{\Delta}\ensuremath{\varepsilon}\ensuremath{\upsilon}\ensuremath{\tau}\ensuremath{\varepsilon}\ensuremath{\rho}o\ensuremath{\beta}\ensuremath{\acute\alpha}\ensuremath{\theta}\ensuremath{\mu}\ensuremath{\iota}\ensuremath{\alpha}\ensuremath{\varsigma}} {E\ensuremath{\kappa}\ensuremath{\pi}\ensuremath{\alpha}\ensuremath{\acute\iota}\ensuremath{\delta}\ensuremath{\varepsilon}\ensuremath{\upsilon}\ensuremath{\sigma}\ensuremath{\eta}\ensuremath{\varsigma}} \ensuremath{\sigma}\ensuremath{\tau}\ensuremath{\eta}\ensuremath{\nu} {K\ensuremath{\acute\iota}\ensuremath{\nu}\ensuremath{\alpha}.}},
     journal = {M\ensuremath{\alpha}\ensuremath{\theta}\ensuremath{\eta}\ensuremath{\mu}\ensuremath{\alpha}\ensuremath{\tau}\ensuremath{\iota}\ensuremath{\kappa}\ensuremath{\acute\eta} E\ensuremath{\pi}\ensuremath{\iota}\ensuremath{\theta}\ensuremath{\varepsilon}\ensuremath{\acute\omega}\ensuremath{\rho}\ensuremath{\eta}\ensuremath{\sigma}\ensuremath{\eta}},
     pages = {78--89},
     year = {1981},
     volume = {24},
     language = {gr},
     url = {http://geodesic.mathdoc.fr/item/MR_1981_24_a18/}
}