The trombone : the instrument and its music / Robin Gregory
New York : Praeger, 1973
Trombone chamber music : an annotated bibliography / by Harry J. Arling. 2nd ed., rev. & enl.
Nashville, TN : Brass Press, c1983
MUSIC Ref ML128.T76 A7 1983
Annotated guide to bass trombone literature / by Thomas G. Everett. 3rd ed., rev. and enl.
Nashville, TN : Brass Press, c1985
MUSIC Ref ML128.T76 E9 1985
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
ITA journal, v. 1 (1972)- ML1.I86; also under earlier title, Journal - International Trombone Association
Newsletter of the International Trombone Association, v. 1 (1974) - 8 (1981) ML1.N765
Brass bulletin--the Library has selected volumes between 1983 and 2003
M - Scores
M90-94--Solo trombone music
M262-263--Music for trombone and piano
M1032-1033, M1132-1133--Trombone with orchestra and string orchestra (includes full scores and solos with piano arrangements)
ML - Music Literature
ML128.T76--Trombone music: Bibliography
ML965-968--Books about the trombone
MT - Instruction and Study
MT460-472--Methods, etudes, orchestra studies, etc.
Trombone and piano music
Concertos (Trombone with string orchestra)
Trombone with orchestra
...and there are lots more. Do a subject search for "trombone" and see the 99 different subject headings that begin with "trombone."
... and lots more. Search "trombone" in Encore and find more than 40 books, more than 300 recordings and more than 750 scores.