“10. Procedure in relation to certain trust properties: In the case of any person referred to in clause (vi) of Explanation 3 to sub-section (2) of section 2, if the competent authority, on the basis of the information and materials available to it, has reason to believe (the reasons for such belief to be recorded in writing) that any property held in trust is illegally acquired property, it may serve a notice upon the author of the trust or, as the case may be, the contributor of the assets out of or by means of which such property was acquired by the trust and the trustees, calling upon them within such time as may be specified in the notice which shall not ordinarily be less than thirty days, to explain the source of the money or other assets out of or by means of which such property was acquired or, as the case may be, the source of the money or other assets which were contributed to the trust for acquiring such property and thereupon such notice shall be deemed to be a notice served under section 6 and all the other provisions of this Act shall apply