Michael Haydn's Symphony No. 11 in B-flat major, Perger 9, Sherman 11, MH 82 and 184, was written in Salzburg in 1766. Hans Gál attributed this work to Joseph Haydn, but he was not the first to do so (Hoboken's catalog lists this as the second symphony in B-flat major so attributed). Movements of it were published as a Joseph Haydn work, in fact, in 1772.[1]
A. Delarte, "A Quick Overview Of The Instrumental Music Of Michael Haydn" Bob's Poetry Magazine November 2006: 18 - 19 PDF
Charles H. Sherman and T. Donley Thomas, Johann Michael Haydn (1737 - 1806), a chronological thematic catalogue of his works. Stuyvesant, New York: Pendragon Press (1993)
C. Sherman, "Johann Michael Haydn" in The Symphony: Salzburg, Part 2 London: Garland Publishing (1982): lxiv - lxv