 Other works produced by Hu 's studio included a reprint of Zhou <unk> 's manual of seal @-@ script calligraphy , The Six Styles of Calligraphy , Correct and Erroneous ( <unk> Zheng 'e , <unk> ) and the related Necessary Investigations into Calligraphy ( <unk> Bi Ji , <unk> ) , which discussed common errors in the formation of characters . With his brother <unk> , Hu edited a new introductory edition of the Confucian classics , entitled The <unk> Text of the Four Books , Identified and Corrected ( <unk> <unk> <unk> , <unk> ) ( 1640 ) , giving the correct formation and pronunciation of the text . A similar approach was taken with the Essentials of the Thousand Character Classic in Six Scripts ( <unk> <unk> <unk> , <unk> ) ( 1663 ) , which Hu compiled with the aid of his calligraphy teacher , Li Deng . It was published after Li 's death , partly in homage to him . 
