(8)For the purposes of this section,—(a)"author" includes a joint author;(b)"books" shall not include brochures, commentaries, diaries, guides, journals, magazines, newspapers, pamphlets, text-books for schools, tracts and other publications of similar nature, by whatever name called;(c)"competent authority" means the Reserve Bank of India or such other authority as is authorised under any law in force for regulating payments and dealings in foreign exchange;(d)"lump sum", in regard to royalties or copyright fees, includes an advance payment on account of such royalties or copyright fees which is not returnable.