I analyzed ~ 480 triliteral roots that have the same 2nd and 3rd radical (quasi biliterals) and treated them as biliteral roots by removing the terminal radical. 3/4 of these radicals had a mirror root (i.e. mn & nm or bt & tb) and 1/4 did not. In other words, biliterals could be divided into one quarter with no mirror, and two 3/8ths that mirror each other.
October 7, 2011