In several places I have come across references to a 2005-6 preprint of Denis Simon entitled 


*Quadratic equations in dimensions 4, 5, and more*


This paper gives fast algorithms to find isotropic vectors in a 4 or 5 dimensional quadratic space over $\mathbb{Q}$, based on indefinite LLL.


I have been unable to get a hold of it. Is it online? Has it been published?



Paper of Denis Simon on quadratic equations in dimensions 4, 5?
It used to be on Simon's website, and [archive.org](https://archive.org/web/) saved a copy:


<http://web.archive.org/web/20061123185700/http://math.unicaen.fr/~simon/maths/Dim4.pdf>


Thanks to Mark Watkins for pointing this out.


I have reached out to Simon to ask about it but haven't heard back, so I don't know an explanation for why he took it down.


