In some work I'm doing I have two graded modules $M$ and $N$ (graded on $\mathbb Z$, say) and need to take, not the usual direct sum, but the bigraded sum consisting of all $M_p \oplus N_q$ (so graded on $\mathbb Z \oplus \mathbb Z$). For the graded sum I would simply write $M\oplus N$. Before I make up a notation for the bigraded sum, is there an already existing notation that anyone has used or seen?
I'm not sure what tags to include on this question, feel free to criticize. I've tried to tag the communities that might have run into this before.