Hi, I just remembered a question I have wondered about for countless of years without finding any answer to: Have (any of) the electric charges of quarks been empirically measured/tested/verified? (Yes, I know about the Standard Model and what the charges are supposed to be, that's not what I'm after. I've searched for it on this forum and on the net, but failed to find any info about empirical tests). If anybody has good info about this and/or good link(s) I'll be very interested to know about it. My regards!