Fixed missing reference

1 files changed, 14 insertions, 0 deletions

diff --git a/guide/guide.bib b/guide/guide.bib
index 601f45f786..697165963b 100644
--- a/guide/guide.bib
+++ b/guide/guide.bib
@@ -2015,3 +2015,17 @@ archivePrefix = {arXiv},
        adsurl = {https://ui.adsabs.harvard.edu/abs/2001AJ....122.3466M/abstract},
       adsnote = {Provided by the SAO/NASA Astrophysics Data System}
 }
+
+@article{StephensonMorrisonHohenkerk:2021,
+       author = {Morrison, L. V.  and Stephenson, F. R.  and Hohenkerk, C. Y.  and Zawilski, M. },
+        title = {Addendum 2020 to \&\#x2018;Measurement of the Earth\&\#x2019;s rotation: 720 BC to AD 2015\&\#x2019;},
+      journal = {Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences},
+       volume = {477},
+       number = {2246},
+        pages = {20200776},
+         year = {2021},
+          doi = {10.1098/rspa.2020.0776},
+          URL = {https://royalsocietypublishing.org/doi/abs/10.1098/rspa.2020.0776},
+       eprint = {https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2020.0776},
+     abstract = { Historical reports of solar eclipses are added to our previous dataset (Stephenson et al. 2016 Proc. R. Soc. A 472, 20160404 (doi:10.1098/rspa.2016.0404)) in order to refine our determination of centennial and longer-term changes since 720 BC in the rate of rotation of the Earth. The revised observed deceleration is −4.59 ± 0.08 × 10−22 rad s−2. By comparison the predicted tidal deceleration based on the conservation of angular momentum in the Sun–Earth–Moon system is −6.39 ± 0.03 × 10−22 rad s−2. These signify a mean accelerative component of +1.8 ± 0.1 × 10−22 rad s−2. There is also evidence of an oscillatory variation in the rate with a period of about 14 centuries. }
+}