Kamlowski, A., B. Altenberg-Greulich, A. van der Est, S.G. Zech, R. Bittl, P. Fromme, W. Lubitz, and D. Stehlik, (1998) The quinone acceptor A1 in Photosystem I: Binding site, and comparison to QA in purple bacteria reaction centers. The Journal of Physical Chemistry B, 102(42):  8278-8287.