For every tempo-move there exists a tempo-try corresponding to it. A hidden tempo-try is defined as a tempo-try that corresponds to none of the tempo-moves of the solution. However, the mentioned correspondence has not been defined rigorously yet. Therefore presently we identify hidden tempo-tries only in the case when the solution does not contain tempo-moves but the problem contains tempo-tries; according to the definition given above all of them are hidden.
Jonsson, Bernt Christer
Tidskrift för Schack, 1982
1st HM
1.Bxg4
e4
2.Bf5
exf5
3.Kh5
fxg6
4.Kh6
gxh7
5.g6
h8=Q#