Here's a summary:
The Westminster Confession of Faith defines the sufficiency of Scripture like this:
The whole counsel of God, concerning all things necessary for his own glory, man's salvation, faith, and life, is either expressly set down in Scripture, or by good and necessary consequence may be deduced from Scripture: unto which nothing at any time is to be added, whether by new revelations of the Spirit, or traditions of men (1:6).
The Thirty-nine Articles of the Anglican Church include this statement on sola Scriptura:
Holy Scripture containeth all things necessary to salvation: so that whatsoever is not read therein, nor may be proved thereby, is not to be required of any man, that it should be believed as an article of the Faith, or be thought requisite or necessary to salvation (article 6).