The above Kassian-Dybo's research did not take into account the findings by Russian linguist Andrey Zaliznyak who stated that, until the 14th or 15th century, major language differences were not between the regions occupied by modern Belarus, Russia and Ukraine, but rather between the north-west (around modern Velikiy Novgorod and Pskov) and the center (around modern Kyiv, Suzdal, Rostov, Moscow as well as Belarus) of the East Slavic territories. The Old Novgorodian dialect of that time differed from the central East Slavic dialects as well as from all other Slavic languages much more than in later centuries. According to Zaliznyak, the Russian language developed as a convergence of that dialect and the central ones, whereas Ukrainian and Belarusian were continuation of development of the central dialects of East Slavs.
tHe aBoVe kaSsian-DybO's reseaRch did not tAke iNTO accouNT the fiNDinGS by russIan lInGuisT anDrey zaliznyaK whO statEd thaT, uNtil ThE 14TH or 15th centuRy, majOR laNguAGE diFferences wERe not bETwEen tHE rEGIoNS OccuPiEd by ModerN belARus, Russia and UkrainE, but raTHer bEtweEn the norTh-wESt (ARouNd ModERN veLIkIy noVgOROd anD psKov) anD tHe CENtER (ArouNd modern kYiv, SUZdaL, roSTOv, MosCow as weLL as BELarus) of tHE east sLavIc tERRitOrIeS. tHE old NoVgorODIan dialEct of ThAt Time difFEreD frOm the cENTral EasT SLAvIc dialeCtS As weLl as fRom AlL OtHer Slavic lanGUages mUch more THaN in LAter CeNTuRieS. aCcordING to zAliznyAk, thE rUSsIaN language dEveloPed AS a conveRGence oF THAT dIaLEcT aNd The centRaL oNes, wherEaS UKraInian And beLarUsian weRE contiNuAtion oF DeVelOpMenT of the cenTRAl DialectS of eAsT SlavS.