Floer's paper, *An Instanton-Invariant for 3-Manifolds*, makes reference to Casson's construction of a topological invariant for homology 3-spheres. He literally references it by placing the bibliographic-tag [C] in one of his sentences... but he doesn't actually list it in the bibliography!  

I subsequently search around, and cannot find where Casson originally defines his invariant; only locate papers that talk about his invariant. Does this "paper" not exist? I would think that such an important construction has a foundational paper in existence.



Seeking a seemingly missing reference of Casson
According to [the following paper](http://projecteuclid.org/DPubS?verb=Display&version=1.0&service=UI&handle=euclid.jdg/1214510050&page=record), this invariant's introduction is sourced as: A. Casson, Lecture notes, MSRI Lectures, Berkeley, 1985.


The first published discussion appears to be found in: S. Akbulut & J. McCarthy, Casson's invariant for oriented homology 3-spheres, an exposition, Math. Notes, No. 36, Princeton Univ. Press, Princeton, 1990.




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"I don't know if he [Casson] has ever written his notes. I attended his lectures at MSRI then I went back to MSU and tried to fill in the details together with McCarthy, those notes are the result." S. Akbulut




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"[Here](https://www.dropbox.com/s/jxe820nij8bcs33/Casson%20notes.PDF) is a pdf of hand-written notes of T. Cochran's. Page two includes annotated notes by Boyer, and I got the notes from my friend and colleague, A. Nicas." H. Boden


