BRITISH publisher Dorling Kindersley reported a big jump in half year earnings thanks to a strong performance from books and CD Roms. Pre tax profits in the six months to the end of December climbed to £8.1 million from £5.3 million in the corresponding period in 1994. The interim dividend is increased by 0.2p to 1.5p on earnings per share of 6.9p against 4.8p.