diff --git a/TODO.txt b/TODO.txt
index 12f1f59..fd720cc 100644
--- a/TODO.txt
+++ b/TODO.txt
@@ -21,4 +21,6 @@ scale each value by per-class thresholds, i.e., [0.33*0.1, 0.33*1, 0.33*1]/sum.
     check https://docs.python.org/3/library/warnings.html#temporarily-suppressing-warnings
 - [TODO] nmd and md are not selectable from qp.evaluation.evaluate as a string
 - [TODO] add https://www.kaggle.com/datasets/Cornell-University/arxiv dataset? in the paper "Online Adaptation to
-    Label Distribution Shift" they say it provides a natural label shift over time
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+    Label Distribution Shift" they say it provides a natural label shift over time
+- [TODO] add Bhattacharyya distance (https://en.wikipedia.org/wiki/Bhattacharyya_distance)
+    (which is actually not a proper distance)
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