@Article{AAM-37-394,
author = {Li , Dong},
title = {On Fractional Smoothness of Modulus of Functions},
journal = {Annals of Applied Mathematics},
year = {2021},
volume = {37},
number = {3},
pages = {394--404},
abstract = {<p style="text-align: justify;">We consider the Nemytskii operators $u\to |u|$ and $u\to u^{\pm}$ in a bounded domain $\Omega$ with $C^2$ boundary. We give elementary proofs of the boundedness in $H^s(\Omega)$ with $0\le s&lt;3/2$.</p>},
issn = {},
doi = {https://doi.org/10.4208/aam.OA-2021-0006},
url = {http://global-sci.org/intro/article_detail/aam/19852.html}
}