[formula] missing statement about content of covered-table-cell informula

Hi all,

when a cell spans two or more columns or rows, than the "hidden" cells 
are of kind "covered-table-cell". Those cells might be empty but they 
can have content as well. I miss a statement, how those cells have to be 
treated, when they are referenced in a formula.
As far as I have tested Gnumeric, Excel, and Openoffice.org Calc, in 
those applications the cells are treated as "normal" cells.

Kind regards
Regina