Johnson, B. A., Shirokawa, J. M., Geddes, J. W., Choi, B. H., Kim, R. C., & Aswad, D. W. (1969). Protein L-isoaspartyl methyltransferase in postmortem brains of aged humans. Neurobiology Of Aging, 12(1), 19-24. https://doi.org/10.1016/0197-4580(91)90034-h (Original work published 1969)