# Acknowledgements

Moon libration data for the years 2020-2022 comes from NASA's Scientific Visualization Studio.

[mooninfo_2020.txt](https://svs.gsfc.nasa.gov/vis/a000000/a004700/a004768/mooninfo_2020.txt)
comes from: [Moon Phase and Libration 2020](https://svs.gsfc.nasa.gov/4768)

[mooninfo_2021.txt](https://svs.gsfc.nasa.gov/vis/a000000/a004800/a004874/mooninfo_2021.txt)
comes from: [Moon Phase and Libration 2021](https://svs.gsfc.nasa.gov/4874)

[mooninfo_2022.txt](https://svs.gsfc.nasa.gov/vis/a000000/a004900/a004955/mooninfo_2022.txt)
comes from: [Moon Phase and Libration 2022](https://svs.gsfc.nasa.gov/4955)

These Moon Phase and Libration pages contain some wonderful videos, images, and explanatory text that
help make the complexities of the Moon's orbit and libration understandable.

# Further Reading

The PDF document [Computation of the Quantities Describing the Lunar Librations
in The Astronomical Almanac](https://astro.ukho.gov.uk/data/tn/naotn74.pdf) provides a
detailed explanation of the meaning of lunar libration quantities like sub-solar angles,
sub-earth angles, and polar position angles.