“…Estimation of CO 2 concentration in 7 of the 19 trials gave poor correlation (Choubert & Baccaunaud, 2006;Emborg, Laursen, Rathjen, & Dalgaard, 2002;Guldager, Boknaes, Osterberg, Nielsen, & Dalgaard, 1998;Pettersen, Nissen, Eie, & Nilsson, 2004;Randell et al, 1995;Torrieri, Cavella, Villani, & Masi, 2006). This poor correlation can have several reasons.…”