diff --git a/fit_a_line/README.md b/fit_a_line/README.md
index 9838667f9272d9a1584bd72db78a6a293bb1fc50..f6611bfe1b8e300b875c0e54c4b9acd4404e33fb 100644
--- a/fit_a_line/README.md
+++ b/fit_a_line/README.md
@@ -169,4 +169,4 @@ python predict.py -m output/pass-00020 -t data/housing.test.npy
 1. https://en.wikipedia.org/wiki/Linear_regression
 2. Friedman J, Hastie T, Tibshirani R. The elements of statistical learning[M]. Springer, Berlin: Springer series in statistics, 2001.
 3. Murphy K P. Machine learning: a probabilistic perspective[M]. MIT press, 2012.
-4. Bishop C M. Pattern recognition[J]. Machine Learning, 2006, 128.
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+4. Bishop C M. Pattern recognition[J]. Machine Learning, 2006, 128.