needed? hmmmmmm...because that was the way it was done... remember replacing judas in Acts?
24And praying, they said: Thou, Lord, who knowest the hearts of all men, shew whether of these two thou hast chosen,
25To take the place of this ministry and apostleship, from which Judas hath by transgression fallen, that he might go to his own place.
26And they gave them lots, and the lot fell upon Matthias, and he was numbered with the eleven apostles.
not a book, but something you might want to peruse http://archive.catholic.com/library/Apo ... ession.asphttp://archive.catholic.com/library/church_papacy.asp