The Gregg Reference Manual was created in 1951.
-"Publication Manual of the American Psychological Association"-"Gregg Reference Manual".
Labor Relations Reference Manual was created in 1937.
According to the Gregg Reference Manual, there is an apostrophe after the final s in Saints: All Saints' Day.1. Sabin, William A. The Gregg Reference Manual. 10th ed.(New York: McGraw-Hill/Irwin, 2005), p. 192.
Gregg Press was created in 1965.
The Gregg School was created in 1901.
Gregg Allman Tour was created in 1974.
Gregg Smith Singers was created in 1955.
Andrew Gregg Homestead was created in 1825.
Gregg's - New Zealand - was created in 1861.
Edward M. Gregg Farm was created in 1914.
Earl Gregg Swem Library was created in 1966.
According to The Associated Press Stylebook and Libel Manual and checking the recommended spellings there against the recommended spellings in William Sabin's The Gregg Reference Manual and The American Heritage Dictionary, it is 2 words. So the correct format is help desk.