b-tree bbbbbb beebee beeper beeter berbee berber bereet berere berrer berret bertre berube betere betete betrue bettee better betutu beurre breere brette breuer brubru bruree bubber bububu burbet burbur burpee burper burree burrer burret burrup burutu butere butter ebbert eburru eebree erbree errett ettutu eutere pberet pebete peepee peeper peerer peeter peetre pepper perere peretu perper perpet perree perret perter pertre peteet peteru petree petrer petter pettet pppppp preeue prepub preter pretre prette preue- pruett pubber puerer puppet pupput purete purpre purpur purree purrer put-up putput putrer puttee putter puttur puture r-tree rebute reeper repete repper repure repuru repute reteer reteet retere retree retret retter rettur retube returu reuere reuter reutte rub-up rubbee rubber rubutu rupert rurutu ruttee rutter rutube t-tree t-tube teebee teepee teerpu teetee teeter tepper terete terper terrer terret terter tertre tetete tetter trebur treete treppe tretee trette truett trueup tubber tuppee tupper turbet turret turtur tururu tuteur tutter tuttut u-tube up-put ureter urette uruppu uteute