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To mention some popular chain codes, they are: Freeman Chain Code of Eight Directions1 (FCCE), Vertex Chain Code2 (VCC), Three OrThogonal symbol chain code3 (3OT) and Directional Freeman Chain Code4 (DFCC).
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 E. Bribiesca, A new chain code, Pattern Recognition 32 (1999) 235–251.
 H. Sánchez-Cruz, R. M. Rodríguez-Dagnino. Compressing bi-level images by means of a 3-bit chain code. Optical Engineering. SPIE. 44 (9) 097004 (2005) 1-8.
 Y.K. Liu, B.Zalik, And efficient chain code with Huffman coding, Pattern Recogni- tion 38 (4) (2005) 553-557.