grounding-dataset: mention MioGatto

resources/grounding-dataset.md

@@ -6,7 +6,7 @@ title: Dataset for Grounding of Formulae
 ### Basic Information
 
 * Author: Takuto Asakura, André Greiner-Petter, Akiko Aizawa, and Yusuke Miyao
-* Updated: 2020-03-26
+* Updated: 2021-04-01
 
 ### Accessibility and License
 
@@ -34,6 +34,10 @@ dataset](/resources/arxmliv-dataset-082018/), and we manually annotated all
 937 identifiers (i.e., `<mi>` tags) in the document to the corresponding
 mathematical objects (meanings).
 
+The annotation is performed with our open-source annotation tool
+[MioGatto](https://github.com/wtsnjp/MioGatto). The tool is also suitable for
+viewing the data. Please refer to its documentation for the details.
+
 ### Download
 
 [Download link](https://gl.kwarc.info/SIGMathLing/grounding-dataset-v1)