505.Changes to the scheme itself cannot be made unless the operator has given notice to the Authority, and the Authority has either approved the proposal, or not notified its disapproval. As for the replacement of the operator, trustee or depositary, at least one month’s notice must be given to the Authority either by the person being replaced, or the person proposing to replace him, but there is no express provision for the Authority to approve or disapprove the replacements.