Simplified building-up principles

A single coronoid formula may be situated in such a place of Table 5.3 (and its extension) that one or two of the formulas C H 2 3 5-1 n—2 s exist. 

These special cases lead to simplifications of the building-up process (cf. also the comment below 

Illustration of the fundamental building-up principle applied to isomers (Principle 6.3). The formulas are arranged as in Table 5.3. 

Principle 6.3). Corresponding simplifications have been discussed for benzenoids by Dias (for references, see Par. 6.5.3) and, more systematically, elsewhere (Cyvin SJ, Cyvin and Brunvoll 1993e). 

Catacondensed Systems. The catacondensed single coronoids fall outside the scope of Principle 6.3. Instead, we have the following rules. 

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