BOLOKHONTSEV, E.N. 1911 Botanical-biological studies of Lake Ladoga In Lake Ladoga as a water supply source for the city of S. Petersburg. Sanitary part. Commission on surveys and studies of Lake Ladoga and its key sources. Saint Petersburg: municipal printing house Pp. 171-585 [Russian] c.f. http://dlib.rsl.ru/viewer/01003532879#?page=5