diff --git a/gtfs-realtime/spec/en/reference.md b/gtfs-realtime/spec/en/reference.md
index 5c482653..f303f027 100644
--- a/gtfs-realtime/spec/en/reference.md
+++ b/gtfs-realtime/spec/en/reference.md
@@ -196,14 +196,14 @@ Realtime update for arrival and/or departure events for a given stop on a trip.
 Updates can be supplied for both past and future events. The producer is allowed, although not required, to drop past events.
 The update is linked to a specific stop either through stop_sequence or stop_id, so one of these fields must necessarily be set.  If the same stop_id is visited more than once in a trip, then stop_sequence should be provided in all StopTimeUpdates for that stop_id on that trip.
 
-In added or replacement trips, updates are used to specify the stops visited by the trip without referring to the GTFS Static. In such trips, `stop_id`, `stop_sequence`, `departure` and `arrival` must all be set.
+In added or replacement trips, updates are used to specify the stops visited by the trip without referring to an existing trip in the GTFS Static. In such trips, `stop_id`, `stop_sequence`, `departure` and `arrival` must all be set.
 
 **Fields**
 
 | _**Field Name**_ | _**Type**_ | _**Required**_ | _**Cardinality**_ | _**Description**_ |
 |------------------|------------|----------------|-------------------|-------------------|
 | **stop_sequence** | [uint32](https://protobuf.dev/programming-guides/proto2/#scalar) | Conditionally required | One | Must be the same as in stop_times.txt in the corresponding GTFS feed.  Either stop_sequence or stop_id must be provided within a StopTimeUpdate - both fields cannot be empty.  stop_sequence is required for trips that visit the same stop_id more than once (e.g., a loop) to disambiguate which stop the prediction is for. If `StopTimeProperties.assigned_stop_id` is populated, then `stop_sequence` must be populated.  For added and replacement trips, this field is compulsory and must be increasing along the trip. |
-| **stop_id** | [string](https://protobuf.dev/programming-guides/proto2/#scalar) | Conditionally required | One | Must be the same as in stops.txt in the corresponding GTFS feed. Either stop_sequence or stop_id must be provided within a StopTimeUpdate - both fields cannot be empty. If `StopTimeProperties.assigned_stop_id` is populated, it is preferred to omit `stop_id` and use only `stop_sequence`. If `StopTimeProperties.assigned_stop_id` and `stop_id` are populated, `stop_id` must match `assigned_stop_id`. For added and replacement trips, this field is compulsory. |
+| **stop_id** | [string](https://protobuf.dev/programming-guides/proto2/#scalar) | Conditionally required | One | Must be the same as in stops.txt in the corresponding GTFS feed. Either stop_sequence or stop_id must be provided within a StopTimeUpdate - both fields cannot be empty. If `StopTimeProperties.assigned_stop_id` is populated, it is preferred to omit `stop_id` and use only `stop_sequence`. If `StopTimeProperties.assigned_stop_id` and `stop_id` are populated, `stop_id` must match `assigned_stop_id`. For added and replacement trips, this field is required. |
 | **arrival** | [StopTimeEvent](#message-stoptimeevent) | Conditionally required | One | If schedule_relationship is empty or SCHEDULED, either arrival or departure must be provided within a StopTimeUpdate - both fields cannot be empty. For added and replacement trips, both must be provided. arrival and departure may both be empty when schedule_relationship is SKIPPED.  If schedule_relationship is NO_DATA, arrival and departure must be empty. |
 | **departure** | [StopTimeEvent](#message-stoptimeevent) | Conditionally required | One | If schedule_relationship is empty or SCHEDULED, either arrival or departure must be provided within a StopTimeUpdate - both fields cannot be empty. For added and replacement trips, both must be provided. arrival and departure may both be empty when schedule_relationship is SKIPPED.  If schedule_relationship is NO_DATA, arrival and departure must be empty. |
 | **departure_occupancy_status** | [OccupancyStatus](#enum-occupancystatus) | Optional | One | The predicted state of passenger occupancy for the vehicle immediately after departure from the given stop. If provided, stop_sequence must be provided. To provide departure_occupancy_status without providing any real-time arrival or departure predictions, populate this field and set StopTimeUpdate.schedule_relationship = NO_DATA. <br><br>**Caution:** this field is still **experimental**, and subject to change. It may be formally adopted in the future. |