Merge branch 'bep046' of github.com:arokem/bids-specification into bep046

Author: arokem

src/derivatives/diffusion-derivatives.md

@@ -14,8 +14,8 @@ the [TRX file format](https://tee-ar-ex.github.io):
                 <source-entities>[space-<space>]_[tract-<tract name>]_[track-<tracking method>]_tractogram.json
 ```
 
-Where `tract` is the anatomical/structural entity that is being imaged, and
-`track` is fully specified in the sidecar as described below.
+Where [`tract-<label>`](../appendices/entities.md#tract) is the anatomical/structural entity that is being imaged, and
+[`track-<label>`](../appendices/entities.md#track) uses as its value one of the items in a controlled vocabulary.
 
 For the most common case, a tractogram will be generated from some DWI data, so
 <modality> will typically be “dwi”. In any case, the <modality> allows to