diff --git a/gogole/indexer/bsbi_indexer.py b/gogole/indexer/bsbi_indexer.py
index b0be4da090303e37965019461a0c378ef51c02b2..cc42790fc626ed8b923c41e05849f54afa6239bf 100644
--- a/gogole/indexer/bsbi_indexer.py
+++ b/gogole/indexer/bsbi_indexer.py
@@ -26,14 +26,17 @@ class BSBIIndexer(Indexer):
         self.tmp_filenames = []
         self.tmp_file_id_seq = itertools.count()
 
-        self.count_documents = 0
+        self.document_norms = dict()
 
         self.INDEX_FILE = '.cache/{}_index'.format(collection_name)
         self.TOKENS_MAP_FILE = '.cache/{}_tokens_map'.format(collection_name)
-        self.DOCUMENTS_MAP_FILE = '.cache/{}_documents_map'.format(collection_name)
+        self.DOCUMENT_NORMS_FILE = '.cache/{}_document_norms'.format(collection_name)
 
         self.status = self.INDEX_STATUS_NOT_CREATED
 
+    def get_collection_size(self):
+        return len(self.document_norms)
+
     def init_token_id_seq(self, start=0):
         self.token_id_seq = itertools.count(start=start)
 
@@ -72,14 +75,22 @@ class BSBIIndexer(Indexer):
         # reset the buffer
         self.buffer = []
 
+    def compute_document_vector_norm(self, counted_tokens):
+        norm = 0
+        for token, count in counted_tokens.items():
+            norm += (1 + math.log10(count))**2
+
+        return math.sqrt(norm)
+
     def add_document_tokens(self, document, counted_tokens):
         doc_id = document.document_id
         # convert tokens to token ids
         token_ids = set()
 
-        self.count_documents += 1
+        self.document_norms[doc_id] = self.compute_document_vector_norm(counted_tokens)
 
         for token, frequency in counted_tokens.items():
+
             token_id = self.find_or_create_token_id(token)
             self.buffer += [(token_id, doc_id, frequency)]
 
@@ -180,12 +191,18 @@ class BSBIIndexer(Indexer):
         with open(self.TOKENS_MAP_FILE, 'wb') as f:
             pickle.dump(self.tokens_map, f, pickle.HIGHEST_PROTOCOL)
 
+        with open(self.DOCUMENT_NORMS_FILE, 'wb') as f:
+            pickle.dump(self.document_norms, f, pickle.HIGHEST_PROTOCOL)
+
     def load_from_cache(self):
         try:
             with open(self.TOKENS_MAP_FILE, 'rb') as f:
-                self.status = self.INDEX_STATUS_CREATED
                 self.tokens_map = pickle.load(f)
 
+            with open(self.DOCUMENT_NORMS_FILE, 'rb') as f:
+                self.document_norms = pickle.load(f)
+
+            self.status = self.INDEX_STATUS_CREATED
             return True
 
         except FileNotFoundError:
diff --git a/gogole/query/boolean_query.py b/gogole/query/boolean_query.py
index 12703161d33e135b5bcdfca6293795ff710712a2..b28f7f8341dc20379e52b438ca7e8e821cdd3f43 100644
--- a/gogole/query/boolean_query.py
+++ b/gogole/query/boolean_query.py
@@ -9,7 +9,7 @@ class BooleanQuery(Query):
          # Assume the expression
         # is in the conjunctive normal form
 
-        last_doc_id = self.collection.indexer.count_documents-1
+        last_doc_id = self.collection.indexer.get_collection_size()-1
 
         and_queries = query.split(self.OPERATOR_AND)
         doc_ids_by_conjunction = list()
diff --git a/gogole/query/vectorial_query.py b/gogole/query/vectorial_query.py
index 54da2eb694f0004121a288d3d5e3f6b830704e3b..71954875c4d455b2b234acc35f7b8496106639ee 100644
--- a/gogole/query/vectorial_query.py
+++ b/gogole/query/vectorial_query.py
@@ -34,7 +34,7 @@ class VectorialQuery(Query):
 
         tf = defaultdict(lambda: defaultdict(int))
 
-        N = self.collection.indexer.count_documents
+        N = self.collection.indexer.get_collection_size()
 
         for token in tokens:
             doc_ids = self.collection.indexer.token_lookup_with_frequency(token)