bo-bo bobr bonon bonou boorn booru borbo born- borno bornu boro- boron boroo borou borro borun bourn brobo bronn broon broun brrrr brunn bruno bruun bubon bunun buono burn- buron buroo burro burru burun nnooo no-no nobob nobuo non-u nonno noonu norbu noron norro norun nu-nu nunon nunun nuoro nurun o-bon o-r-b oboro onoon onorn onour ooooo ornon orobo orono oruro ouoro ourno ro-ro robbo robo- robon robor robun robur ronno rorbu rubon rubor runo- runon ubobo unnun unnur unoor unorn unrun unurn uroob urour urubu uuuuu