-tree b-r-k bbbee be-er bebek beber beebe beeft beeke beete beeut beffe befur beker bekke berbe berek beret berk- berke berre berru berte betee beter betke betre bett- bette beuer beure beute brebu breef breek breer breet breke brere brett breu- brrrr bruer bruet bruff bruke brute btr-t bubbe buber bufet buffe buker buket bukk- burek buret burke burru burte burtt buruk burut buter butke butte butut ebber ebbet ebert ebure eeeee ef-tu efere efetf effer effet efter efuru efutu ekker ekuku ekuru erbbe erber erere errtu erte erter eruke eteke etete etree etrek etter eturu eurre febre feere feret ferr- ferre ferte feter fette feuer feute freek freer freet freke frere frett freur frute ftrtt fu-fu futur k-t-b k-ute kebbe kebek keber keefe keere kefee kerek keret kerre kertu ketek keter kette kreef kreek kreke krete kreuk kruft kubek kuber kukur kurbu kurek kurku kurre kurte kuruk kutte kuttu kutur rebbe reber rebet rebut reefe reeft reere refer refet reffe refut rekke rere- reree reret retee reter rette reuer reuet reute rt-rk rubee ruber rubke ruere ruete ruffe rukke ruter rutte ruutu tbtbt tbutt teber tebet tebuk tefe teket tekke terek teret tereu terre tert- teter tetr- tette trbuk treer treet trefe treff trere trete trett treut trubu truer truff truke trute ttttt tubek tuber tuffe tufte tukur turbe turbt turek turet turku turre turtu turut tutee tutku tutte tuuru uber- ufere ukeke ukert urker urkut urter urubu urutu uter- utter uttur utube uturu uuuuu