I have an assumption but I am not pretty sure. Does 'no difference' is the subject of the next sentence?
If so, how can it be a subject with no + difference?
The result was that no difference between base-oriented and object-oriented software could be measured over maintainability.
As @relaxing indicates that I actually want to know the subject of the subordinate clause,so we have found that!.
So again, how can it be a subject with no + difference?