bbbb bobb bobo bobu bomb bomu boob boom boor bor- borm boro borr boru boum bour bovo brob brom broo bror brou brrm brrr brum bruv brvm bubb bubo bubu bum- bumb bur- burb burm buro burr buru mbou mmmm mmor mobb mobo momo momu moob moor moov morb moro moru mour mrbb mrbm mubo mumm mumo mumu muro murr muru obbo obor obro ombo ombu omo- omoo omor omov omro omuo oooo orbb orbo orbu ormo oro- orom oror orro orub orum orvr our- ouro ouu- ovo- ovoo ovum rbbb rbbr rmmv rmvb rob- robb robo robu romb romm romo roob room roor roro roru roub roum rovo rrrr rrum rubb rubu rumb rumm rumo ruro ruru ruvu ubbo umb- umbo ummo umor uomo uor- uovo uro- urom uroo urum urur uuuu uv-b uvvu voom voor vor- vorm voro voru vour vurb vvob vvvv