Authors who have written more than one book

You need to output the full names of those authors who have written more than one book. Authors without books and with only one book are not included in the result.

CREATE TABLE authors (
    id INT PRIMARY KEY,
    fullname VARCHAR(128) NOT NULL
);

CREATE TABLE books (
    id INT PRIMARY KEY,
    title VARCHAR(128) NOT NULL,
    author_id INT REFERENCES authors(id)
);