@Article{CMR-37-i,
author = {},
title = {Preface: Special Issue Dedicated to Professor Roger Penrose's 90th Birthday},
journal = {Communications in Mathematical Research },
year = {2021},
volume = {37},
number = {4},
pages = {i--ii},
abstract = {},
issn = {2707-8523},
doi = {https://doi.org/10.4208/cmr.2021.v37n4.preface},
url = {http://global-sci.org/intro/article_detail/cmr/19436.html}
}