I saw the roshei teivos החזו"א in the Dirshu notes to Mishna Berura in Hilchos Rosh Hodesh. Can you tell me who it is? Is there a general resource to figure this out?
I suspect that that refers to the Chazon Ish. The letters fit, and the Chazon Ish's rulings are often quoted alongside those of the Mishna Berura.