@inproceedings{inproceedingsb0cc90a4,
title   = {Helium abundances in planetary nebulae: nucleosynthesis and chemical evolution},
author = {Maciel, Walter Junqueira and Costa, Roberto Dell'Aglio Dias da and Idiart, Thais Eunice Pires},
year = {2010},
publisher = {Cambridge University Press},
booktitle   = {IAU Symposium}
}