O_tmd = e_tmd_to_t.get(0);
// <b>f</b> <- FORWARD(<b>f</b>, e<sub>t-d</sub>)
f = forward(f, O_tmd);
// <b>B</b> <-
// <b>O</b><sup>-1</sup><sub>t-d</sub><b>B</b><b>T</b><b>O</b><sub>t</sub>
B = O_tmd.inverse().times(hmm.getTransitionModel().inverse())
.times(B).times(hmm.getTransitionModel()).times(O_t);
} else {
// else <b>B</b> <- <b>BTO</b><sub>t</sub>
B = B.times(hmm.getTransitionModel()).times(O_t);
}