-er eee eep eer ees eet eex ep- epe epp epr eps ept epx ere erp err ers ert es- ese esp esr ess est esx ete etp etr ets ett etx ex- exe exp exr exs ext exx p-p pee pep per pes pet pex ppe ppp ppr pps ppt ppx pre prp prr prs prt prx ps- pse psp psr pss pst psx pt- pte ptp ptr pts ptt ptx pxe pxr pxs pxt re- ree rep rer res ret rex rpe rpp rpr rps rpt rpx rrp rrr rrs rrt rse rsp rsr rss rst rsx rte rtp rtr rts rtt rtx rxp rxr rxs se- see sep ser ses set sex spe spp spr sps spt spx sr- sre srp srr srs srt srx ss- sse ssp ssr sss sst ssx ste stp str sts stt stx sxs sxt t-x te- tee tep ter tes tet tex tpe tpp tpr tps tpt tpx tre trp trr trs trt trx tse tsp tsr tss tst tsx tte ttp ttr tts ttt ttx txe txs txt xee xep xer xes xet xex xpe xpp xps xpt xrt xrx xsp xss xst xtp xtr xts xtx xxp xxx