-er eee eeo eep eer eet eex eo- eoe eoo eop eor eot ep- epe epo epp epr ept epx ere ero erp err ert ete eto etp etr ett etx ex- exe exo exp exr ext exx oee oeo oep oer oet oex oo- ooo oop oor oot oox op- ope opo opp opr opt opx or- ore oro orp orr ort orx ot- ote oto otp otr ott ox- oxo oxt oxx p-p pee peo pep per pet pex poe poo pop por pot pox ppe ppo ppp ppr ppt ppx pre pro prp prr prt prx pt- pte pto ptp ptr ptt ptx pxe pxr pxt re- ree reo rep rer ret rex roe roo rop ror rot rox rpe rpo rpp rpr rpt rpx rrp rrr rrt rte rto rtp rtr rtt rtx rxp rxr t-x te- tee teo tep ter tet tex to- toe too top tor tot tox tpe tpo tpp tpr tpt tpx tre tro trp trr trt trx tte tto ttp ttr ttt ttx txe txt xee xep xer xet xex xoo xop xor xot xox xpe xpo xpp xpt xrt xrx xtp xtr xtx xxo xxp xxx