Wow. No idea, but then it was four or more decades ago.
I was a frequent flyer at the local library, and there came a magic age (can't remember what it was) when I was suddenly allowed out of the children's corner and into to the main library, where I discovered anthologies of Asimov, Ellison, and others which I consumed like my life depended on it. (Later, the school library introduced me to many, many more, and this whole pocket-money thing linked up with bookshops...)
So, it was probably Asimov. Or maybe Ellison. But hey, I was only about ten.