Johnson, B., Shirokawa, J., Geddes, J., Choi, B., Kim, R., & Aswad, D. (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)