effere effete effutu efreet efter- erfurt erketu errett ettutu eutere fekete ferfer ferrer ferret ferrur fertee fertek ferter fetter feture feuter frefre frette freure fterer fterre fuerte furfur furrer furrfu futret futter future k-tree keefer keeffe keeker kekkut kereft kereru kerker kerkuk kertee ketter ketuke keuruu krefft kreker kretek kukere kurree kururu kutke kutter r-tree reefer reeffe reeker refeet refeff refert refete refret refter refute rekrut reteer reteet retere retree retret retter rettur returf returu reuere reuter reutte rufete ruffer ruffet rufter rukutu rurkee rurutu ruttee rutter t-tree teetee teeter tekrur terete terrer terret terter tertre tetete tetter treete trefet trefte treker tretee trette tretuk truett trufte truker tuffet tufter tuktuk turfer turker turret turtuk turtur tururu tuteur tutter tuttut ufreet ureter urette uruffe uteute utukku utukur