Table: race_results_15
Columns: year
entrant
chassis
engine
points

Question: What is the Chassis having a year later than 1990, and Minardi Scuderia Italia as an entrant, and 4 points?
SQL: SELECT "chassis" FROM race_results_15 WHERE "year" > 1990 AND "entrant" = 'minardi scuderia italia' AND "points" = 4