Water vapour at high redshift: Arecibo monitoring of the megamaser in MG J0414+0534 P. Castangia, C. M. V. Impellizzeri, J. P. McKean, C. Henkel, A. Brunthaler, A. L. Roy, O. Wucknitz, J. Ott and E. Momjian A&A, 529 (2011) A150 Published online: 22 April 2011 DOI: 10.1051/0004-6361/201016403