An SAB advisory letter indicates that many members of the Council believe that the Chestnut and Rowe study is the best available.
The SAN advisory has stated that it does not believe the Chestnut and Rowe study is the best. 
mnli hypothesis: The SAN advisory has stated that it does not believe the Chestnut and Rowe study is the best.  premise: An SAB advisory letter indicates that many members of the Council believe that the Chestnut and Rowe study is the best available.