Viewpoints is a collection of teachings by members of the First Presidency and the Quorum of Twelve Apostles - those men we sustain as prophets, seers, and revelators - on various subjects. Where talks or articles are written, generally the entire presentation is given in PDF or some other format so that the reader may read everything in context. When the sources in question are books, however, only the pertinent passages are quoted. Some of the views may be somewhat divergent from each other, but in every case we must maintain this standard put in the words of Joseph Fielding Smith:
It makes no difference what is written or what anyone has said, if what has been said is in conflict with what the Lord has revealed, we can set it aside. My words, and the teaching of any other member of the Church, high or low, if they do not square with the revelations, we need not accept them. Let us have this matter clear. We have accepted the four standard works as the measuring yardsticks, or balances, by which we measure every man's doctrine.
(Joseph Fielding Smith, Doctrines of Salvation, 3:203.)
The Lord has given us the four Standards which lie at the foundation of our faith. Each member of the Church should be so well versed that he, or she, would be able to discern whether or not any doctrine taught conforms to the revealed word of the Lord. Moreover, the members of the Church are entitled, if they are fully keeping the commandments and covenants the Lord has given us, to have the spirit of discernment. The fact remains, however, that too many of the members have not taken advantage of their blessings and obligations, and therefore they are unable to distinguish between truth and error. The "Lay" members of the Church are under obligation to accept the teachings of the authorities, unless they can discover in them some conflict with the revelations and commandments the Lord has given.
(Joseph Fielding Smith, Answers to Gospel Questions, 2:112.)