Some very common contracted labels cannot be interpreted with a simple application of valence rules, but also need some implicit charges to be added. Others may represent slightly unusual bonding patterns. The labels shown below may be freely used within contracted labels; however, since they all have only a single point of attachment, the textual strings shown below should always be the last (or only) text within a label or within a parenthesized portion of a label.
The central rings in the examples below are provided simply as scaffolds to which these labels are attached. Both left-to-right and right-to-left forms of the label are shown
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