CREATE TABLE table_6011 ("Type" TEXT, "wheelbase" TEXT, "M39 series" TEXT, "M809 series" TEXT, "M939 series" TEXT)

Name the M939 series with M809 series of m817 and M39 series of m51
SELECT "M939 series" FROM table_6011 WHERE "M809 series" = 'm817' AND "M39 series" = 'm51'
SELECT "M939 series" FROM "table_6011" WHERE "M39 series" = 'm51' AND "M809 series" = 'm817'