CREATE TABLE table_name_38 (isbn_uk VARCHAR, author VARCHAR, isbn_us VARCHAR)

What is ISBN UK, when Author is 'Dave Martin', and when ISBN US is 'N/A'?
SELECT isbn_uk FROM table_name_38 WHERE author = "dave martin" AND isbn_us = "n/a"
SELECT "isbn_uk" FROM "table_name_38" WHERE "author" = "dave martin" AND "isbn_us" = "n/a"