“Between 1939 to 1945” is obviously incorrect to most people—it should be “between 1939 and 1945”—but the error is not so obvious when it is written thus: “between 1939-1945.” In this case, the “between” should be dropped altogether. Also incorrect are expressions like “there were between 15 to 20 people at the party.” This should read “between 15 and 20 people.”
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