We adhere to the convention that 0/0=0.
We adopt throughout the convention that compact spaces are Hausdorff.
We adopt the convention that the first coordinate i increases as one goes downwards, and the second coordinate j increases as one goes from left to right.
We make the convention that f(Q)=i(Q).
We regard (1) as a mapping of S2 into S2, with the obvious conventions concerning the point ∞.
By convention, we set a(x,y)=0 if no such spaces exist.
This sort of tacit convention is used throughout Gelfand theory.