Na-O anticorrelation and horizontal branches - IV. Detection of He-rich and He-poor stellar populations in the globular cluster NGC 6218E. Carretta, A. Bragaglia, R. G. Gratton, G. Catanzaro, F. Leone, E. Sabbi, S. Cassisi, R. Claudi, F. D'Antona, P. François, G. James and G. PiottoA&A, 464 3 (2007) 939-951DOI: https://doi.org/10.1051/0004-6361:20065730
