Notes on Annotations. I sometimes try also to explain idiosyncratic terminology, in order to make it easier to read the original item. It is normally finite unless otherwise indicated. Sigma is a signed graph. Phi is a gain graph.
Omega is a biased graph.
I cannot name all the people who have contributed advice and criticism, but many of the annotations have benefited from suggestions by the authors or others and a number of items have been brought to my notice by helpful correspondents. I am very grateful to you all. Thanks also to the people who maintain the invaluable MR and Zbl. A code in lower case means the topic appears implicitly but not explicitly. In a string of codes a colon indicates subcategorization.