Online Etymology Dictionary, © 2010 Douglas Harper
Examples from the Web for sidenote
Sidenote: Keeping the Booker election off the November card can't hurt state and local GOP candidates, either.Voter Suppression, Chris Christie Style
June 4, 2013
Where the sidenote precedes a paragraph, it is given on a separate line.A New Voyage to Carolina
Page 85 sidenote: Expression in Painting and Sculpture is a borrowd quality.A Letter on Shakspere's Authorship of The Two Noble Kinsmen
Page 147 (sidenote), year changed to years (Dr. Balliet on the early years of childhood).
Page 189 (sidenote), religous changed to religious (Result to the child of religious acts).
When the location did not change over several pages, only one sidenote was used.The Diary of John Evelyn, Volume II (of 2)