CREATE TABLE table_46139 ("Title" TEXT, "Author" TEXT, "ISBN UK" TEXT, "ISBN US" TEXT, "TV companions featured" TEXT)

What is ISBN UK, when Author is 'Dave Martin', and when ISBN US is 'N/A'?
SELECT "ISBN UK" FROM table_46139 WHERE "Author" = 'dave martin' AND "ISBN US" = 'n/a'
SELECT "ISBN UK" FROM "table_46139" WHERE "Author" = 'dave martin' AND "ISBN US" = 'n/a'