-er eee eer ees eet eex ere err ers ert es- ese esr ess est esx ete etr ets ett etx ex- exe exr exs ext exx re- ree rer res ret rex rrr rrs rrt rse rsr rss rst rsx rte rtr rts rtt rtx rxr rxs se- see ser ses set sex sr- sre srr srs srt srx ss- sse ssr sss sst ssx ste str sts stt stx sxs sxt t-x te- tee ter tes tet tex tre trr trs trt trx tse tsr tss tst tsx tte ttr tts ttt ttx txe txs txt xee xer xes xet xex xrt xrx xss xst xtr xts xtx xxx