@article{Sacha2019PNAS,
publisher = {National Academy of Sciences},
doi = {10.1073/pnas.1913075116},
title = {Time crystal minimizes its energy by performing Sisyphus motion},
url = {https://www.pnas.org/content/116/38/18755},
journal = {Proceedings of the National Academy of Sciences},
author = {Sacha, Krzysztof and Hannaford, Peter},
volume = {116},
year = {2019},
pages = {18755--18756},
number = {38},
eprint = {https://www.pnas.org/content/116/38/18755.full.pdf},
issn = {0027-8424}
}