Shibo Liu. On the Regularity of Operators Near a Regular Operator. The American Mathematical Monthly, 117(10):927-928, 2010. [doi]
@article{Liu10-92, title = {On the Regularity of Operators Near a Regular Operator}, author = {Shibo Liu}, year = {2010}, url = {http://www.jstor.org/stable/10.4169/000298910X523425}, researchr = {https://researchr.org/publication/Liu10-92}, cites = {0}, citedby = {0}, journal = {The American Mathematical Monthly}, volume = {117}, number = {10}, pages = {927-928}, }