D’Orazi, V., Campbell, S. W., Lugaro, M., Lattanzio, J. C., Pignatari, M., & Carretta, E. (2013). On the internal pollution mechanisms in the globular cluster NGC 6121(M4): Heavy-element abundances and AGB models. Monthly Notices of the Royal Astronomical Society, 433(1), 366-381. https://doi.org/10.1093/mnras/stt728