The abundance of HCN in circumstellar envelopes of AGB stars of different chemical type F. L. Schöier, S. Ramstedt, H. Olofsson, M. Lindqvist, J. H. Bieging and K. B. Marvel A&A, 550 (2013) A78 Published online: 30 January 2013 DOI: 10.1051/0004-6361/201220400