diff --git a/doc/0.getting_started.md b/doc/0.getting_started.md
index cd97ea4..8014d2c 100644
--- a/doc/0.getting_started.md
+++ b/doc/0.getting_started.md
@@ -106,7 +106,8 @@ under the `constraints` key. The available constraints are:
 * `postal_codes` is a list of postal codes. You should include any postal code
   you want, and especially the postal codes close to the precise location you
   want.
-* `time_to` is a dictionary of places to compute travel time to them.
+* `time_to` is a dictionary of places to compute travel time to them (using
+  public transport, relies on [Navitia API](http://navitia.io/)).
   Typically,
 
   ```