Gilberto Ramalho, Kazuo Tsushima. A simple relation between the gamma N -> N(1535) helicity amplitudes, article, September 1, 2011; (https://digital.library.unt.edu/ark:/67531/metadc830117/m1/1/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, digital.library.unt.edu; .