Duridanov's cognates of the reconstructed Dacian words are found mostly in the Baltic languages, followed by Albanian without considering Thracian. Parallels have enabled linguists, using the techniques of comparative linguistics, to decipher the meanings of several Dacian and Thracian placenames with, they claim, a high degree of probability. Of 74 Dacian placenames attested in primary sources and considered by Duridanov, a total of 62 have Baltic cognates, most of which were rated "certain" by Duridanov. Polomé considers that these parallels are unlikely to be coincidence. Duridanov's explanation is that proto-Dacian and proto-Thracian speakers were in close geographical proximity with proto-Baltic speakers for a prolonged period, perhaps during the period 3000–2000 BC. A number of scholars such as the Russian Topоrov have pointed to the many close parallels between Dacian and Thracian placenames and those of the Baltic language-zone – Lithuania, Latvia and in East Prussia (where an extinct but well-documented Baltic language, Old Prussian, was spoken until it was displaced by German during the Middle Ages).