Microsoft .Net PetShop 4.0

Can someone tell why Microsoft removed the original documentation about the .net petshop 4.0?

I remember that there was a detailed description about the architecture component by component. Now it has been summarized at this url Microsoft .NET Pet Shop 4: Migrating an ASP.NET 1.1 Application to 2.0 And they (MS) uploaded the source code at Pet Shop Source Codeplex without no more information.

Does anyone have a link about the explained article about this product? or tell why this has been limited to developers?