https://19january2021snapshot.epa.gov/sips-ok/oklahoma-sip-ok-252100-3-air-quality-standards-and-increments-sip-effective-2000-01-03-okc48_.html
Oklahoma SIP: OK 252:100- 3. Air Quality Standards and Increments, SIP effective 2000-01-03 (OKc48)...
Aug 4, 2020 - Oklahoma SIP: OK 252:100- 3. Air Quality Standards and Increments, SIP effective 2000-01-03 (OKc48) to 2009-02-26