Extended envelopes around Galactic Cepheids - IV. T Monocerotis and X Sagittarii from mid-infrared interferometry with VLTI/MIDIA. Gallenne, A. Mérand, P. Kervella, O. Chesneau, J. Breitfelder and W. GierenA&A, 558 (2013) A140DOI: https://doi.org/10.1051/0004-6361/201322257