Guide to the euphonium repertoire : the euphonium source book / compiled and edited by Lloyd E. Bone, Jr. and Eric Paull under the supervision of R. Winston Morris
Bloomington, IN : Indiana University Press, c2007
MUSIC Ref ML128.B24 G83 2007
An annotated bibliography of selected contemporary euphonium solo literature by American composers / by David Miles
[U.S.] : Tuba Press, c1992
MUSIC ML128.B24 M5 1992
The tuba family / by Clifford Bevan. 2nd ed. rev., enl. and updated.
Winchester : Piccolo, 2000
MUSIC ML970.B48 2000
University of Iowa music source book : wind and percussion materials / [faculty members of the University of Iowa School of Music]
[Iowa City] : Paul Anderson, 1986
MUSIC Ref ML128.W5 I48 1986x
ITEA journal, v. 29 (2002)- ML1.T82
T.U.B.A. Journal, v. 4 (1976)-28 (2001) ML1.T82
Brass bulletin--the Library has selected volumes between 1983 and 2003 ML5.B6864
M - Scores
M110.B33--Solo euphonium or baritone music
M270.B37--Music for euphonium or baritone and piano
M1034.B37, M1134.B37--Baritone or euphonium with orchestra and string orchestra (includes full scores and solos with piano arrangements)
ML - Music Literature
ML128.B24--Euphonium music: Bibliography
ML970-973--Books about the tuba, baritone, etc.
MT - Instruction and Study
MT496--Methods, etudes, orchestra studies, etc. for baritone or euphonium
Euphonium and piano music
Suites (Euphonium and piano)
Concertos (Euphonium with band)
...and there are more. Do a subject search for "euphonium" and see the 37 different subject headings that begin with "euphonium."
... and more. Search "euphonium" in Encore and find 12 books, 32 recordings and 84 scores.