Experimental and theoretical investigations of type b coherent creation of electron-positron pairs in aligned crystals by high energy photons; International symposium on radiation of relativistic electrons in periodical structures, Sept. 6-10, Tomsk - Andreyshkin M. Yu.; Kunashenko Yu. P. Yuriy Petrovich; Pivovarov Yu. L. Yuriy Leonidovich; Zabaev V. N. Viktor Nikolaevich (1993, 1993)