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

Please show the most common publication date.
SELECT publication_date FROM publication GROUP BY publication_date ORDER BY COUNT(*) DESC LIMIT 1
SELECT "publication_date" FROM "publication" GROUP BY "publication_date" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 1