bbbb bnor bnrr bobb bobo bobu bonn bono bonu boob boon boor bor- born boro borr boru boun bour bovo brno brob bron broo bror brou brrr brun bruv bubb bubo bubu bunb bunn buno bunu buon bur- burb burn buro burr buru nbbo nnnn nobo nobu non- nonn nono nonu noo- noob noon nooo noor noov nor- norb norn noro norr norv noun nour nov- novo nron nunn nuno nuon nurn nurr nuru nurv nuvo obbo obon obor obro onno onon onor onur oooo orbb orbo orbu orno oro- oron oror orro orub orvr oun- our- ourn ouro ouu- ovo- ovon ovoo rbbb rbbr rnbr rob- robb robo robu rono roob roon roor roro roru roub roun rovo rrrr rrun rubb rubu runn runo ruro ruru ruun ruvu ubbo ubon unno unon unov unro uor- uovo uro- uroo urun urur uuno uuuu uv-b uvvu vonn voor vor- voro voru voun vour vrnn vron vuno vurb vvob vvvv