bo-bo bobr bobup boort booru borbo boro- boroo borot borou borro borup borut botou botro bottu bouto brobo broto brout brrrr btr-t buroo burro burru burtt burut buto- butor butot butou butuo butut o-r-b oboro obout ooooo opobo opto- optot optto orbot orobo orout ortoo oruro orutu ototo otour otpor ottur oubut ouoro outro outto po-po poopo poort popop poppo popup poro- porro porto portu porur potoo potop potor potro potto pottu probo proor proot prop- propp propr propt prot- proto prout prtor ptprb ptpro ptprr ptprt ptpru pubo- puppo puro- putor putt- putto puttu putuo putup ro-ro robbo robo- robop robor robot robrt robur rorbu roto- rotor rotot rotto roubt routt rprop rptor rubor rubup ruutu t-pop t-top tbtbt tbutt tobor tobot tobou topbt topo- topor topot toppo toptb topto topup torob torpo torro torto tortu toto- totoo totop totup touro tprot troop trop- tropo trott troup trout trubu trupt truro ttttt tubo- tubou tuotu tupou turbo turbt turot turro turtu turup turut tutor tutto tuuru u-pop ubobo upput uptop uroob urour urubu urutu utro- utrop utror uttur uturu ututo uuuuu