Eldon offered Dwight F. some advice for working on intonation with another hornist. Specifically, he recommended Verne Reynolds' "Intonation Exercises for Two Horns."
I have often been in the position of correcting the dubious intonation of those around me, and I think that the Reynolds lacks the heft required to have a significant effect on out-of-tune players. For this purpose, I much prefer the New Grove Dictionary of Music. These volumes fit easily into your throwing hand; the covers are easily gripped without risk of slipping; the volumes are bulky enough to minimize the influence of air resistance; they produce a satisfying acoustical result when they collide with the persons and/or instruments of those whose intonation requires improvement; and the New Grove comes in many volumes, so that one or two may be left over for your reading pleasure after you have improved the intonation of everyone within reach.
So if you really want to make an impact on the intonation of those around you, it is hard to beat the New Grove Dictionary for range and accuracy.
Gotta go,
Cabbage