From Guy Gardner: Reborn #2, August 1992:
This was after Hal Jordan had kicked Guy out of the Green Lantern Corps, forcing him to find another power source. He’d gone to Qward, with Lobo in tow, looking to get a yellow power ring just like the one the Qwardians had made for Sinestro all those years before.
Trouble is . . .
That’s right – Sinestro’s ring used up all the Qwardamite on the planet which means it can never be duplicated!
Oh, hang on . . .