@misc{_Walerian,
 copyright={Public Domain},
 howpublished={online},
 title={Walerian Bętkowski},
 type={Image},
 URL={http://rcin.org.pl/Content/77075/PDF/WA058_90700_Betkowski_W.pdf},
 keywords={Bętkowski, Walerian (1899-1964), naturalists, botanists, teachers, metodologists, environmental activists},
}