(a) Controlling persons
Every person who, by or through stock ownership, agency, or otherwise, or who, pursuant to or in connection with an agreement or understanding with one or more other persons by or through stock ownership, agency, or otherwise, controls any person liable under sections 77k or 77l of this title, shall also be liable jointly and severally with and to the same extent as such controlled person to any person to whom such controlled person is liable, unless the controlling person had no knowledge of or reasonable ground to believe in the existence of the facts by reason of which the liability of the controlled person is alleged to exist.

(b) Prosecution of persons who aid and abet violations
For purposes of any action brought by the Commission under subparagraph (b) or (d) of section 77t of this title, any person that knowingly or recklessly provides substantial assistance to another person in violation of a provision of this subchapter, or of any rule or regulation issued under this subchapter, shall be deemed to be in violation of such provision to the same extent as the person to whom such assistance is provided.