The clumpiness of molecular clouds: HCO+ (3–2) survey near Herbig-Haro objects W. Whyatt, J. M. Girart, S. Viti, R. Estalella and D. A. Williams A&A, 510 (2010) A74 Published online: 12 February 2010 DOI: 10.1051/0004-6361/20078350