diff --git a/3.4.-pri-request=stations_available.md b/3.4.-pri-request=stations_available.md
index 5c27b66..991d47a 100644
--- a/3.4.-pri-request=stations_available.md
+++ b/3.4.-pri-request=stations_available.md
@@ -15,13 +15,21 @@
 | description   | o        | text<=20 | short station description                             |
 | gps           | +        | array     | GPS: latitude, longitude                           |
 | station       | +        | text  | station prefix_number                                 |
-| station_group | +        | array  | station group  |
+| station_group | +        | array  | station_group describes which bike_groups are allowed at the station |
 | authed          | o        | text  | return 1 if user is authenticated on operator |
 | gps_radius    | +        | text     | geofencing by meters around station, for bike return. |
 | uri_operator          | +        | text  | URI of operator-server                 |
 | bike_count | + | text | Amount of available bikes on station |
 | operator_data | o | object | operator values (see example) |
 
+
+**station_group** describes which **bike_groups** are allowed at the station.
+Groups are identified by ID. The following groups of bicycles are defined:
+| group ID | bike type |
+| ------ | ------ |
+| 300101 | Cargobike |
+| 300103 | Citybike |
+
 Example
 **REST request=stations_available** for authorized users
 ```