Klukas, O., W.-D. Schubert, P. Jordan, N. Krauß, P. Fromme, H.T. Witt, and W. Saenger, (1999) Localization of two phylloquinones, QK and QK′, in an improved electron density map of photosystem I at 4-Å resolution. Journal of Biological Chemistry, 274(11): 7361-7367.