diff --git a/doc/src/CNN/cnn.do.txt b/doc/src/CNN/cnn.do.txt
index 2cd2aed0e..bc992de48 100644
--- a/doc/src/CNN/cnn.do.txt
+++ b/doc/src/CNN/cnn.do.txt
@@ -9,6 +9,8 @@ DATE: today
 * update codes to tensorflow 2
 * add more elaborated examples
 * update keras codes and think of pytorch examples?
+* Example on pollen cases  https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0229751
+
 !split
 ===== Convolutional Neural Networks (recognizing images) =====