20 CFR 702.419: Action by employer upon acquiring knowledge or being given notice of injury.

Whenever an employer acquires knowledge of an employee's injury, through receipt of a written notice or otherwise, said employer shall forthwith authorize, in writing, appropriate medical care. If a form is prescribed for this purpose it shall be used whenever practicable. Authorization shall also be given in cases where an employee's initial choice was not of a specialist whose services are necessary for and appropriate to the proper care and treatment of the compensable injury or disease. In all other cases, consent may be given upon a showing of good cause for change.