SELECT T2.name FROM rating AS T1 JOIN reviewer AS T2 ON T1.rid = T2.rid GROUP BY T1.rid HAVING COUNT(*) >= 3
Find the names of all reviewers who have contributed three or more ratings.
CREATE TABLE reviewer (
    rid number,
    name text
)

CREATE TABLE rating (
    rid number,
    mid number,
    stars number,
    ratingdate time
)

CREATE TABLE movie (
    mid number,
    title text,
    year number,
    director text
)