bbbb bbbs bblb bbls blls blss blub blur blus brls brrr brrs brsb brsr brus bubb bubs bubu bulb bull buls bulu bur- burb burl burr burs buru buss busu buus lblr lbrs llbs llll lrrr ls-r lsbu lssr lubs lull lulu lurs luss rbbb rbbr rbbs rbsl rbss rlls rrrr rssl rubb rubs rubu rull rurs ruru russ rusu sbbs sbus slrs slsu slub slur srub ssbr ssrl ssrs sssb ssss sub- subb subl subs sul- sull sulu sur- surr surs suru sus- suss susu suus ubls ullr ulul ulus urbs urls urss ursu urur urus usbl usbr usbs uslu ussb ussr usss ussu usul usus uulu uuuu