Update readme

README.md

@@ -3,7 +3,7 @@
 ![Pattern example](doc/leader.png)
 
 The [**FGDC Digital Cartographic Standard for Geologic Map
-Symbolization**][fgdc_std], released in 2006, provides guidance and
+Symbolization**](fgdc_std), released in 2006, provides guidance and
 assets for the preparation of geologic maps. It includes a large array
 of reference styles for geologic linework and map symbology.
 
@@ -12,11 +12,14 @@ SVG and PNG, for use on the modern web. This can be paired with collections of
 linework and geologic symbols for the construction of slick geologic maps and
 stratigraphic columns.
 
-Additionally, I provide the symbols as brushes for the iPad drawing app
-*Procreate*, which can be used for laying out stratigraphic columns.
+Additionally, this package includes
+a catalog of brushes for the iPad drawing app
+[*Procreate*](procreate), which supports the sketching
+of geologic maps and stratigraphic columns.
 
 See the [**DOCUMENTATION**](documentation) for usage and next steps.
 
 [fgdc_std]: https://ngmdb.usgs.gov/fgdc_gds/geolsymstd/download.php
 [documentation]: http://davenquinn.com/projects/geologic-patterns
+[procreate]: https://procreate.art