(a) On and before April 17, 2012, the terms used in this subpart are defined in the Clean Air Act; Secs. 61.02 and 61.61 of this chapter; and Sec. 63.2 for terms used in the applicable provisions of subpart A of this part, as specified in Sec. 63.11143(b).
(b) After April 17, 2012, terms used in this subpart are defined in the Clean Air Act; Sec. 63.2; and Sec. 63.12005. [77 FR 22906, Apr. 17, 2012]