Examples from the Web for a2
A2 seemed the most promising, but A3 could also have potential, so I would carry these two options on to the next level.A Mathematically Impossible Novel: Manil Suri Explains “The City of Devi”|Manil Suri|March 15, 2013|DAILY BEAST
Title with ornament containing an open book, A2 (verso blank).
Let us next examine the eighth term (A2) and see how it is formed.An Introduction to the Study of the Maya Hieroglyphs|Sylvanus Griswold Morley
There is, to aid imagination, a definite corporal effect due to a2 slight change in the nature of the air.Switzerland|Frank Fox
At the surface of the ground there is no inequality of level—the beds overlying the coal (a2) having been removed by denudation.Fragments of Earth Lore|James Geikie
The values of a2 at the various stations differ comparatively little, and show but little seasonal change.