CREATE TABLE publication (publication_id DECIMAL, book_id DECIMAL, publisher TEXT, publication_date TEXT, price DECIMAL)
CREATE TABLE book (book_id DECIMAL, title TEXT, issues DECIMAL, writer TEXT)

List the publication dates of publications with 3 lowest prices.
SELECT publication_date FROM publication ORDER BY price LIMIT 3
SELECT "publication_date" FROM "publication" ORDER BY "price" NULLS FIRST LIMIT 3