Jerry Blinn closed AviSys in August 2015 and passed away in November 2015 without leaving any provision for continuity of AviSys. Ownership of his website, avisys.net, expired and it is no longer in operation. I have preserved relevant pages from the website here, with some additional material, including annual Clements taxonomic updates for 2016–2019.
These are the additional materials that are provided here:
There was not a 2020 Clements update. The next Clements update is planned for August 2021 so expect the AviSys update mid to late August 2021.
In case you would like to make your own taxonomic updates, I have preserved Jerry's EditMaster program here.
Here are some additional documents that may be of interest.