Section 25B(3)(a) in The Delhi Rent Control Act, 1958
(a)The Controller shall, in addition to, and simultaneously with, the issue of summons for service on the tenant, also direct the summons to be served by registered post, acknowledgment due, addressed to the tenant or his agent empowered to accept the service at the place where the tenant or his agent actually and voluntarily resides or carries on business or personally works for gain and may, if the circumstances of the case so require, also direct the publication of the summons in a newspaper circulating in the locality in which the tenant is last known to have resided or carried on business or personally worked for gain.