A Search for Differential Rotation in Cool Stars Using Ca II H and K Emission Porter, A. C. ; Baliunas, S. L. ; Horne, J. H. ; Noyes, R. W. ; Duncan, D. K. ; Frazer, J. ; Lanning, H. ; Misch, A. ; Mueller, J. ; Soyumer, D. ; Vaughan, A. H. ; Woodard, L. Abstract Publication: Bulletin of the American Astronomical Society Pub Date: January 1985 Bibcode: 1985BAAS...17..512P