Special degenerate single coronoid

Definition 2.2 A special degenerate single coronoid is a d enerate single coronoid where the edge(s) not belonging to hexagons are common to the outer boundary and the hole. 

Two of them ( 2 22 26 22 special degenerate single coronoids, while the other... 

In the case of special degenerate single coronoids, as well as in single (nondegenerate) coronoids, one speaks about the outer and inner perimeter, viz. C and C", respectively, but now some edge(s) belong to both C fl C" 0. 

Definition 2.S A generalized single coronoid is either a single coronoid or a special degenerate single coronoid. 

If one wants to avoid the term "special degenerate single coronoid", then one has the synonymous designation "degenerate generalized single coronoid" at hand. 

In the first case (i) of the above diagram, the effective units are four benzenoids (two pyrenes and two benzenes) in case (ii) the effective units are two benzenoids (anthracenes) and one coronoid (kekulene) in case (iii) the effective units are two benzenoids (naphthalenes) and one special degenerate single coronoid (condensed [18]annulene, viz. hexabenzo[6cdc/,fcim7io][18]-annulene). 

In I—Fig. 2.4 the three systems of the upper row are not special d enerate coronoids, but this is the case for the bottom system. Here are four additional examples of degenerate single coronoids ... 

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