John R. Levine, Paul E. Hoffman. Variants in Second-Level Names Registered in Top-Level Domains. RFC, 6927:1-18, May 2013. [doi]
@article{rfc6927, title = {Variants in Second-Level Names Registered in Top-Level Domains}, author = {John R. Levine and Paul E. Hoffman}, year = {2013}, month = {May}, doi = {10.17487/RFC6927}, url = {https://doi.org/10.17487/RFC6927}, researchr = {https://researchr.org/publication/rfc6927}, cites = {0}, citedby = {0}, journal = {RFC}, volume = {6927}, pages = {1-18}, }