VizieR online Data Catalogue associated with article published in journal Astronomical Journal (AAS) with title 'The Helix Nebula viewed in HCO^+^: large-scale mapping of the J=1->0 transition.' (bibcode: 2013ApJ...778...16Z)
Zeigler, N. R. (Creator), Zack, L. N. (Creator), Woolf, N. J. (Creator), Ziurys, L. M. (Creator) (2015). Observations of HCO^+^ in NGC 7293. Centre de Donnees Strasbourg (CDS). 10.26093/cds/vizier.17780016