(1) A nomination made under sub· regulation (2) ofregillation 3 may Subsequently be substituted or cancelled.
(2) Every nomination, substitirtion of nomination or cancellation of nomination shall be made to the National Housing Bank in such form as may be specified by the National Housing Bank ru:td. shall be accompanied with the relevant bond or deposit receipt.
(3) Receipt of a valid nomination, substitution of nomination or cancellation of nomination shall be acknowledged in writing to the concerned bondholder or depositor by the National Housing Bank,'The nomination, substitution of nomination or cancellation of nomination' shall be deemed to be effective from the date of such acknowledgement by the National Housing Bank. The National Housing Bank may also make a suitable endorsement about the nomination, substitution of nomination or cancellation of nomination on the bond or deposit receipt
(4) The substitution of nomination or cancelIation of nomination shall not be vaiid in the case of a'bond or deposit held jointly h1 more than vuc bondholder or depcsitcr unle3S such substitution or cancellation is made by all the surviving bondholder(s) or depositor(s).