UNIGRAM T:%t
UNIGRAM U1:%F[0]
UNIGRAM U2:%F[0],%F[1]
UNIGRAM U3:%F[0],%F[1],%F[2]
UNIGRAM U4:%F[0],%F[1],%F[2],%F[3]
BIGRAM B1:%L[0]/%R[0]
BIGRAM B2:%L[0],%L[1]/%R[0],%R[1]
BIGRAM B3:%L[0],%L[1],%L[2]/%R[0],%R[1],%R[2]
BIGRAM B4:%L[0],%L[1],%L[2],%L[3]/%R[0],%R[1],%R[2],%R[3]