WITHDRAWN: The effectiveness of diaphragmatic breathing relaxation training for improving sleep quality among nursing staff during the COVID-19 outbreak: a before and after study

The Publisher regrets that this article is an accidental duplication, at the publisher's end, of an article that has already been published in Sleep Medicine doi:10.1016/j.sleep.2020.12.003. The duplicate article has therefore been withdrawn.

The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.