CREATE TABLE table_13856 ("Date" TEXT, "Label" TEXT, "Format" TEXT, "Country" TEXT, "Catalog" TEXT)

From what catalog was the release that happened on April 12, 1968, and in LP format?
SELECT "Catalog" FROM table_13856 WHERE "Format" = 'lp' AND "Date" = 'april 12, 1968'
SELECT "Catalog" FROM "table_13856" WHERE "Date" = 'april 12, 1968' AND "Format" = 'lp'