Richard D. Mabry, "Some remark[s] concerning the uniformly gray sets of G. Jacopini", Rend. Acc. Naz. Sci. XL, Mem. Mat., vol. XXII (1998), fasc. 1, pagg. 43-49 [ISSN: 0392-4106]. My copy is here:PDF; I recently noticed that an official version is on the journal's website: the journal's website  .

This paper was a hasty reply to an article in the Bulletin of the Italian Academy of Sciences (if I may translate it suchly). Professor Jacopini described how "gray" (grigio) sets can be constructed. I had done this earlier and wanted my propriety recognized! But I also took issue with one of his claims or interpretations.

In my haste I made a pretty dumb error in a proof, as was pointed out to me a few months or years later by my former student, Keith Neu, who has picked up the shading mantle and proven many nice things. I don't quite recall the error now, but it was a cardinality issue. Anyway, the proof was overdone anyway; I could have more easily quoted a result of Kakutani and Oxtoby in their famous 1950 paper, but I wanted to do it my way. Lesson learned. (I should have been especially careful in the proofs, since the paper was accepted 24 hours after it was received! Tsk. And I even missed the typo in the title: "some remark" should be "some remarks". It sounds so sarcastic in the singular!)