Section 4A. During the course of the annual listing of residents, the registrars shall notify residents of the opportunity to register as voters and shall provide residents with assistance in registering to vote. Said registrars may, for this purpose provide to such residents in the course of such listing, forms for affidavits of voter registration prescribed by the state secretary pursuant to section thirty-six, which registrants shall complete during the listing or by return mail. Said registrars shall in any event make such forms available upon request for all eligible residents who are not registered voters.