The phrase 'Miller sources' refers to cassettes/reels/dats etc of Grateful Dead live shows (both aud and sbd) which have been mastered and put into lossless trader circulation by Charlie Miller. They are not albums and they are not officially released by the GD. Charlie does such a great job of mastering these unofficial sources. His 'releases' (for want of a better term) are just about always the definitive versions of the shows in question. His reputation is such at this point that the phrase 'Miller source' is a hallmark of quality for collectors of GD shows.