Feuerstein, J., Kalbitzer, H. R., John, J., Goody, R. S., & Wittinghofer, A. (1987). CHARACTERIZATION OF THE METAL-ION - GDP COMPLEX AT THE ACTIVE-SITES OF TRANSFORMING AND NONTRANSFORMING P21 PROTEINS BY OBSERVATION OF THE (O-MN)-O-17 SUPERHYPERFINE COUPLING AND BY KINETIC METHODS. EUROPEAN JOURNAL OF BIOCHEMISTRY, 162(1), 49-55. doi:10.1111/j.1432-1033.1987.tb10540.x.