@Article{CMR-37-4, 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 = {0--0}, abstract = {}, issn = {2707-8523}, doi = {https://doi.org/10.4208/cmr.2021.v37n4.preface}, url = {https://global-sci.com/article/81513/preface-special-issue-dedicated-to-professor-roger-penroses-90th-birthday} }