It is important to note that in 325 a great conference of Christian theologians and religious scholars was convened in the city of Nicaea under the order of the Emperor Constantine to examine and define the status of these books. After thorough investigation it was decided that the Epistle of Jude was genuine and believable. The rest of these books were declared doubtful. This was explicitly mentioned by Jerome in his introduction to his book.
Another council was held in 364 in Liodicia for the same purpose. This conference of Christian scholars and theologians not only confirmed the decision of the council of Nicaea regarding the authenticity of the Epistle of Jude but also declared that the following six books must also be added to the list of genuine and believable books: The book of Esther, The Epistle Of James, The Second Epistle of Peter, The Second and Third Epistles of John, The Epistle of Paul to the Hebrews. This conference pronounced their decision to the public. The book of Revelations, however, remained out of the list of the acknowledged books in both the councils.
In 397 another great conference was held called the Council of Carthage. Augustine, the great Christian scholar, was among the one hundred and twenty six learned participants. The members of this council confirmed the decisions of the two previous Councils and also added the following books to the list of the divine books : The Book of the Songs of Solomon, The Book of Tobit, The Book of Baruch, Ecclesiastics, The First and Second Books of Maccabees.
At the same time the members of this council decided that the book of Baruch was a part of the book of Jeremiah because Baruch was the deputy of Jeremiah. Therefore they did not include the name of this book separately in the list.
Three more conferences were held after this in Trullo, Florence and Trent. The members of these meetings confirmed the decision of the Council of Carthage. The last two councils, however, wrote the name of the book of Baruch separately.
After these councils nearly all the books which had been doubtful among Christians were included in the list of acknowledged books.