Sings observations of spiral galaxies evidence for secular evolution

Michael Regan, Michele D. Thornley, Stuart N. Vogel, Kartik Sheth, Bruce T. Draine, David J. Hollenbach, Martin Meyer, Daniel A. Dale, Charles W. Engelbracht, Robert C. Kennicutt, Lee Armus, Daniela Calzetti, Karl D. Gordon, George Helou, Claus Leitherer, Sangeeta Malhotra, George H. Rieke, Marcia J. Rieke