Van Snick, J., Uyttenhove, C., Van Pel, A., & Boon, T. (1981). Stimulation of Cytolytic T Lymphocytes By Azaguanine-resistant Mouse-tumor Cells in Selective Hat Medium. Journal of Immunological Methods, 46(3), 321-326. https://doi.org/10.1016/0022-1759(81)90317-3 (Original work published 1981)