Can all double summations be rewritten as a single sum?
For example, can this, , be rewritten as a single sum, and if so, how?
The answer isn't important this is just an example.
Edit: I stand corrected. But I probably won't be of much further help in this discussion.. I am familiar with Kronecker Delta but don't see how it relates to the question, also it's been years since I used Green's Theorem and I don't really remember it.