Section 17
SEC. 17. The omission by accident or mistake of the prescribed notice from a particular copy or copies shall not invalidate the copyright or prevent recovery for infringement thereof, against any person who, after actual notice of the copyright, begins an undertaking to infringe it, but shall prevent the recovery of damages against an innocent infringer who has been misled by the omission of the notice; and in a suit for infringement no permanent injunction shall be had unless the copyright proprietor shall reimburse to the innocent infringer his reasonable outlay innocently incurred if the court, in its discretion, shall so direct.