If you've tried to install the SCSM 2016 and 1801 authoring tool, you have probably been looking for a place to download the Visual Studio 2008 Shell Redist because the link in the prereq check is broken. The product group has recently re-released the authoring tool with these bits included so that customers do not have to go hunt for it on the internet. 
The downloads to the authoring tools are below:
2016: https://www.microsoft.com/download/details.aspx?id=54059
1801: https://www.microsoft.com/download/details.aspx?id=56561