diff --git a/docs/user-guide/grid-formats.rst b/docs/user-guide/grid-formats.rst
index 4b89844ca..021f04786 100644
--- a/docs/user-guide/grid-formats.rst
+++ b/docs/user-guide/grid-formats.rst
@@ -221,7 +221,7 @@ References
 * https://easy.gems.dkrz.de/Processing/healpix/index.html#hierarchical-healpix-output
 * https://healpix.sourceforge.io/
 * https://irsa.ipac.caltech.edu/healpix/
-* https://iopscience.iop.org/article/10.1086/427976
+* https://doi.org/10.1086/427976
 
 Parsed Variables
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