bbbb bbox bibb bibi bibo bio- bioi biot biox birb biri biro birr birt birx bito bitt bitx bixi bobb bobi bobo boi- boii boit boob boor boot boox bor- bori boro borr bort botb boti boto bott brio brit brix brob broo bror brot brox brrr btob btor btrt bttb ibot ibox ibri ibro ibtb iiii iiio iiit iioi iioo iitr iitt iobi ioii ioio ioit iooi iooo iori ioto iri- irio irix irob irri irti itoi itoo itor itri itto ixxi obbo obit obix oboi obor obot obox obri obro oiii oirt oiti oobi oooo oort ootb orbb orbi orbo ori- orio orit orix oro- oror orot orri orro orto otit oto- otoo otor otro otti otto oxi- oxo- oxox oxxo rbbb rbbr rib- ribo riot riri riti rito ritt rixo rob- robb robi robo robt roio roir roit roob rooi roor root roox rori roro rort roti roto rotr rott roxo rrrr tbit tbox tbrb tibi tiit tirb tiri tiro tirr titi tito titt tixt tobi tobo tobt toit toor toot tori toro torr tort torx toti toto totr tott tox- toxi toxo toxt tri- trib trio trit trix troi troo trot trox trtr ttbb tttt txii txtr xbox xibo xiii xito xixi xoro xoxo xtro xxii xxix xxxi xxxo xxxx