bbbb bbbs bibb bibi bibo bibs biis bio- bioi bios birb biri biro birr birs bis- biso biss bivi bobb bobi bobo bobs boi- boii bois boob boor boos bor- bori boro borr bors bosi boso boss bovi bovo brio bris brob broo bror bros brrr brrs brsb brsr brvi bsos ibis ibos ibri ibro ibss iiii iiio iiis iioi iioo iios iirs iisi iisr iobi ioii ioio iooi iooo ioos iori iors ioso iri- irio iris irob irov irri irrs irvs isis iso- isor isos isri issi isso issr isss ivbv ivor ivrs obbo obis oboi obor obos obri obro obsr obss obvi obvs oiii oios oobi oooo ooos oosi orbb orbi orbo orbs ori- orio oris oro- oror oros orri orro orrs orsi orso orvr orvs osii osis osoi osoo osor osos osov osro ossb ossi osso ovi- ovis ovo- ovoo rbbb rbbr rbbs rbis rbss rib- ribo ribs riis rios riri rirs risi riso riss rivo rivs rob- robb robi robo robs roio roir rois roob rooi roor roos rori roro rosi roso ross rovi rovo rovs rrrr rsbi rsis rsos s-ib s-ii s-iv s-os sbbs sbor sbsi sibi sibo sibs sior sios siri siro sirr sirs sisi siss sivi sobo sobr sobs soir sois soor soos sorb sori soro sorr sors sosi soso soss sosv sovo sovs srib sris sros ssbr ssis ssri ssrs sssb sssi ssss svir svor vibs viii vios virb viri viro virr visi viso viss vivi vivo voio voir vois voor vor- vori voro vors vosi voso voss vrio vris vrsi vvob vvsb vvvv