Publisher
- oxford university press / usa8
- american association for the advancement of science7
- elsevier inc.7
- nature publishing group uk7
- uppsala universitet, institutionen for fysik och astronomi6
- caltech, pasadena, ca 91125 usa.5
- charles univ prague, prague, czech republic.5
- harvard smithsonian ctr astrophys, cambridge, ma 02138 usa.5
- leiden univ, leiden, netherlands.5