In the Technical Guidelines the "arrow over" only shows a right-pointing arrow (see p.72) in the example for vectors. What about a left-pointing arrow, or a double arrow (east/west)? Why isn't this shown inside the grouping symbols?
I intend to use: AB(156) + arrow symbol (without any grouping symbols). - unless you have a better suggestion. That means the arrow over symbol on p. 72 will not be used because that arrow would be very different from the normal symbols I'll use for the left and double arrows.
This is an example of an INCOMPLETE code. It is frustrating to have to hunt for the simplest things then find nothing suitable. Transcriber defined indicators (which I'm not fond of) have already been used for other things.