Does the Russian song "Dorogoy Dlinoyu" usually include the "ta da da da dum da" part that Mary Hopkin includes in her version of TWTD?   Not sure if Gene Raskin did it that way, but the Limeliters did not. When I first heard Mary Hopkin's recording, after being introduced to the song by the Limeliters, I was struck by the similarity of that refrain -- its format, feeling and sound -- to Edith Piaf's recording of "Milord," which I had become familiar with in the early '60s. It seemed very derivative to me -- almost copycat.   I must admit I have no way of knowing how common that sort of belted out "ta da da da" reprise was, but that part of TWTD does resemble the melody of the chorus of "Milord" a lot.

Of course, It's possible Piaf (and her songwriters/arrangers) "borrowed" from the Russian folk song, rather than the other way around.