1. Variation of the average penumbra-umbra ratio of sunspots during the solar cycle Creator: Dezsö, L. and Gerlei, O. Format: bez média and svazek Type: model:article and TEXT Subject: heliophysics, solar cycle, and penumbra-umbra ratio of sunspots Language: Czech Rights: http://creativecommons.org/publicdomain/mark/1.0/ and policy:public