Where the World Wildlife Fund, India makes sales of educational materials, that is to say, greeting cards, calenders, posters, post cards, picture sets, note pad, gift tag, or any other material which contains its logo and carries theme or message to educate people about the importance of conservation of nature, such dealer may, for the purpose of determination of turnover of sales on which tax is payable, deduct under clause (c) of sub-section (1) of section 16, from its turnover of sales that part of turnover of sales which represents the sales of such educational materials, and it shall, no demand by the appropriate authority under the Act, furnish the relevant tax invoice, invoice, cash memo or bill, as the case may be.