user: Question: What team's champion has a secondary class of Matt Rao for a Winter Series Champion of Not Held?
Columns: ['Season', 'Champion', 'Constructor', "Teams' Champion", 'Secondary Class', 'Nations Cup', 'Winter Series Champion']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['1976', 'David Kennedy', 'Van Diemen', 'Not Held', 'Not Held', 'Not Held', 'Not Held']
SQL:

assistant: SELECT "Teams' Champion" FROM "Table" WHERE "Winter Series Champion" = 'Not Held' AND "Secondary Class" = 'Matt Rao';