We discuss phenomenon of simultaneous presence of O- and C-based material in surroundings of evolutionary advanced stars. We concentrate on silicate carbon stars and present observations that directly confirm the binary model scenario for them. We discuss also class of C-stars with OH emission detected, to which some [WR] planetary nebulae do belong.
@article{arxiv.0704.0557,
title = {Mixed chemistry phenomenon during late stages of stellar evolution},
author = {R. Szczerba and M. R. Schmidt and M. Pulecka},
journal= {arXiv preprint arXiv:0704.0557},
year = {2007}
}