Sørensen, T. (1936). "Some ecosystemtical characteristics determined by Raunkiær's circling method". Nordiska (19. skandinaviska) naturforskarmötet i Helsingfors den 11-15 augusti 1936: 474–475. "To designate the fundamental unit of ecological plant sociology I propose the term ecotope, viz. the field delimited as an object of investigation within a given ecosystem (Tansley)" /wiki/Thorvald_S%C3%B8rensen