-er eee eef eem eeo eer eet eex ef- efe eff efm efo efr eft efx em- eme emf emm emo emr emt emx eo- eoe eof eom eoo eor eot ere erf erm ero err ert ete etf etm eto etr ett etx ex- exe exo exr ext exx fee fef fem feo fer fet fex ffe fff ffm ffo ffr fft ffx fme fmf fmm fmo fmr fmt fmx foe fof fom foo for fot fox fre frf frm fro frr frt fte ftf ftm fto ftr ftt ftx fxe fxm fxr fxt fxx m-f m-o m-r mee mef mem meo mer met mex mfe mff mfm mfo mfr mft mme mmf mmm mmo mmr mmt mmx moe mof mom moo mor mot mox mre mrf mrm mro mrr mrt mrx mte mtf mtm mto mtr mtt mtx mxr oee oef oem oeo oer oet oex of- ofe off ofm ofo ofr oft ofx om- ome omf omm omo omr omt omx oo- oof oom ooo oor oot oox or- ore orf orm oro orr ort orx ot- ote otf otm oto otr ott ox- oxf oxo oxt oxx re- ree ref rem reo rer ret rex rfe rff rfm rfo rfr rft rme rmf rmm rmo rmr rmt rmx roe rof rom roo ror rot rox rrf rrm rrr rrt rte rtf rtm rto rtr rtt rtx rxr t-x te- tee tef tem teo ter tet tex tfe tff tfm tfo tfr tft tfx tme tmf tmm tmo tmr tmt tmx to- toe tof tom too tor tot tox tre trf trm tro trr trt trx tte ttf ttm tto ttr ttt ttx txe txf txt xee xem xer xet xex xfe xfm xft xfx xmf xmm xmo xmr xmt xmx xof xom xoo xor xot xox xrf xrt xrx xtf xtm xtr xtx xxo xxx