b-tree bbbbbb beebee beefer beerze beeter beezer befree befret berbee berber bereet bereft berere berrer berret bertre betere betete bettee better betzet breefe breere breeze brette ebbert eebree effere effete efreet efter- erbree errett etrez ferber ferez ferfer ferrer ferret ferrez fertee ferter fetter fetzer freeez freeze frefre frette fterer fterre r-tree reefer reeffe refeet refeff refert refete refret refter reteer reteet retere retree retret retter t-tree teebee teetee teeter terete terfez terrer terret terter tertre terzet tetete tetter treete trefet trefte tretee trette tzetze zeebee zerbet zertz zezere