CREATE TABLE table_30520 ("Letters" TEXT, "Organization" TEXT, "Nickname" TEXT, "Founding Date" TEXT, "Founding University" TEXT, "Type" TEXT, "Canadian Chapters" TEXT)

When are the letters what is the nickname?
SELECT "Nickname" FROM table_30520 WHERE "Letters" = 'ΚΑΘ'
SELECT "Nickname" FROM "table_30520" WHERE "Letters" = 'ΚΑΘ'