Section 35(6)(b) in The Air (Prevention and Control of Pollution) Assam Rules, 1991
(b)Where the person to served is an officer serving Government if the document is addressed to the person and a copy thereof is to be endorsed to his Head of Department and also Secretary to the Government, as the case may be, in charge of the department in which for the time being the matter relating to the Department which the officer is transacted and is either-