[ Installation, repair, maintenance, and operation for others of drilling machines and drilling tools in connection with drilling oil and gas wells; installation, repair, maintenance, and operation for others of pumping systems for conveying drilling tools and logging tools in connection with drilling oil or gas wells; installation, repair, maintenance, and operation for others of drills, drill bits, drill heads and drill strings in connection with drilling oil or gas wells ]

[ Installation, repair, and maintenance of drilling machines and drilling tools in connection with drilling oil and gas wells for others; drilling of oil or gas wells for others; installation, repair, and maintenance of pumping systems for conveying drilling tools and logging tools in connection with drilling oil or gas wells for others; installation, repair, and maintenance of drills, drill bits, drill heads, and drill strings in connection with drilling oil or gas wells for others ]