How to know if a cell is referred in formulas of other cells?

I want to delete some cells, but I want to make sure that these cells are not referenced in formulas of other cells.
How do I do that?

I think there is an option in Menu/Tools/Detective/Trace dependents [Shift+F5].

Also you can search for a reference to the cell with Menu/Edit/Find

Thanks! Trace Dependents is great, Edit->Find & Replace then search in Formulas works too.