add placeholder for eventual publication

src/common-principles.md

@@ -85,7 +85,7 @@ saved under a particular filename specified in the standard. This standard
 aspires to describe a majority of datasets, but acknowledges that there will be
 cases that do not fit. In such cases one can include additional files and
 subdirectories to the existing directory structure following common sense. For example
-one may want to include eye tracking data in a vendor specific format that is
+one may want to include eye-tracking data in a vendor specific format that is
 not covered by this standard. The most sensible place to put it is next to the
 continuous recording file with the same naming scheme but different extensions.
 The solutions will change from case to case and publicly available datasets will

src/introduction.md

@@ -172,6 +172,10 @@ For example:
 
 -   (publication forthcoming)
 
+#### Eye-tracking
+
+-   (publication forthcoming)
+
 ### Research Resource Identifier (RRID)
 
 BIDS has also a