sero serr sers sert sesc sese seso sess sest set- setc sete setf seto sets sett sfcc sfco sfcs sfer sffc sfor sfos sfrc sfro sfss sfts skee skeo sker skes sket skfc skoe skor skot skrt skss soce sock soco socr socs soec soeo soes sofo soft soke sokk soko soof sook soor soos soot sore soro sorr sors sort sose soso soss sost sotc sote sotk soto sots srcc srct srec sreo sres srfc sros srtr sscc ssce sscs ssec ssee sses sset ssfc ssoc ssot ssrc ssrs sssc sssf ssss sstc ssts stcc stcs stec stee stef stek steo ster stes stet stfc stks stoe stof stok stoo stor stos stot strc stre strk stro strs stsf stss sttc sttr tccc tcfc tcos tctc tcts teck teco tecr tecs tect teec teef teek teer tees teet tefc teff teft teke teok teor teos ter- terc tere terf terk tero terr ters tesc tese teso tess test tete teto tetr tets tett tfec tfot tfrs tfss tftc tkof tkos tkts toce tock toco toee toek toer toes toet toff tofo toft toke toko toof took toor toos toot torc tore torf tork toro torr tors tort tosc tose tosk toso toss tost totc tote toto totr tots tott trcc tre- trec tree tref trek treo tres tret trfc trfr troc troe troo tros trot trst trtc trte trtr tscc tsec tses tset tsfc tsks tsos tsse tssf tssr tsst tstc tsts tteo tter ttfc ttff ttoe ttss tttt