"The Society's vice president, Fred Franz, was acknowledged as the organization's principal Bible scholar. On a number of occasions I went to his office to inquire about points. To my surprise he frequently directed me to Bible commentaries, saying, "Why don't you see what Adam Clarke says, or what Cooke says," or, if the subject primarily related to the Hebrew Scriptures, "what the Socino commentaries say."
If you notice as you read on it was by their research and study in "commentaries" and he says they were products of scholars of other religions. To his suprise he found the facts were written in the eighteenth century, worthwhile and very accurate and compared to their own publications which became out of date.