Question about the Letor Resource of Learning to Rank Click Data Mining in GSOC 2017

Hello,

I am YuLun Cai，current in the first year of Master in BeiJing University of
Posts and Telecommunicaitons.I am familiar with Java/Python/C++. I have
also done relevant courses
on Information Retrieval and Machine Learning. I have previous experience
about search engine: use the elasticsearch search engine to build a data
analysis and retrieval system as my final project in Web Search Engine
course.

I looked at various ideas that are offered for GSOC 17 in XaPian. The one
that is of great interest to me is Learning to Rank Click Data Mining. So I
am reading the resources provided in the idea list.But I found that the
resource link  "
http://research.microsoft.com/en-us/um/beijing/projects/letor/"  redirect
to another web page but not the letor project.I guess that the project's
URL has changed. I found some relevant URLs but not sure which one is
correct: https://www.microsoft.com/en-us/research/search/?q=letor
https://www.microsoft.com/en-us/download/details.aspx?id=52482
https://www.microsoft.com/en-us/research/project/mslr/ .