In many cases however, the 2D structure of sugars, peptides, proteins, or oligonucleotides is described by letter codes for sugars, amino acids, or nucleotides and not with full structure image representations. Thus, in US patent documents we find special sequence files in complex work units (CWU) files. For example, RGD stands for the tripeptide H-Arg-Gly-Asp-OH or arginylglycylaspartic acid. However, none of the present OCSR tools were able to recognize such chemistry from images that contain such sequence codes. Instead, rule based systems together with optical character recognition are currently enabling the extraction of such polymeric structures from text but are outside the scope of this work.