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The title phrase, in this case Igor Rivin, should be set in bold at its first appearance (usually in the first sentence).
Don't use so many capital letters in section headings. The first letter in the heading should be capital except when there's some special reason why it shouldn't be, and the later initial letters should be in lower case except when there's a reason to capitalize them (e.g. a person's name, etc.).
Somthing like "Periodic Graphs (Geometry)" is not an appropriate title for a Wikipedia article (in fact it's a redirect page to an appropriately titled article). The appropriate title is Periodic graph (geometry), with lower-case initials (except when there's an occasion to capitalize them, and that doesn't apply in this case) and a singular noun "graph". Plurals are used as article titles only when there's a reason for them; titles are presumptively singular.