Maybe it's the monthly rankings where they provide a link. Here's the general statement they put at the bottom of each weekly ranking:
How is the ranking calculated?
The world ranking is based on teams' achievements over the past year (with severe decay in points throughout each month), recent form over the last 2 months and performance at the last 10 LAN events.
All of that is predicated around a 3-man core each team is required to have in order to retain their past points. Online matches and tournaments are included, but with a diminishing factor which means they cannot make a big difference among the top teams, and mainly serve to put new teams on the map.