Question: Information:  - Montreal Locomotive Works (MLW) was a Canadian railway locomotive manufacturer which existed under several names from 1883 to 1985, producing both steam and diesel locomotives. For a number of years it was a subsidiary of the American Locomotive Company. MLW's headquarters and manufacturing facilities were located in Montreal, Quebec.  - A locomotive or engine is a rail transport vehicle that provides the motive power for a train. The word originates from the Latin "loco"  "from a place", ablative of "locus", "place" + Medieval Latin "motivus", "causing motion", and is a shortened form of the term "locomotive engine", first used in the early 19th century to distinguish between mobile and stationary steam engines.  - A train is a form of rail transport consisting of a series of vehicles that usually runs along a rail track to transport cargo or passengers. Motive power is provided by a separate locomotive or individual motors in self-propelled multiple units. Although historically steam propulsion dominated, the most common modern forms are diesel and electric locomotives, the latter supplied by overhead wires or additional rails. Other energy sources include horses, engine or water-driven rope or wire winch, gravity, pneumatics, batteries, and gas turbines. Train tracks usually consist of two running rails, sometimes supplemented by additional rails such as electric conducting rails and rack rails, with a limited number of monorails and maglev guideways in the mix. The word 'train' comes from the Old French "trahiner", from the Latin "trahere" 'pull, draw'.  - A classification yard (American and Canadian English) or marshalling yard (British, Hong Kong, Indian, Australian and Canadian English) is a railway yard found at some freight train stations, used to separate railway cars on to one of several tracks. First the cars are taken to a track, sometimes called a "lead" or a "drill". From there the cars are sent through a series of switches called a "ladder" onto the classification tracks. Larger yards tend to put the lead on an artificially built hill called a "hump" to use the force of gravity to propel the cars through the ladder.  - A switcher or shunter (Great Britain: "shunter"; Australia: "shunter" or yard pilot; United States: "switcher", switch engine, or yard goat, except Pennsylvania Railroad: shifter) is a small railroad locomotive intended not for moving trains over long distances but rather for assembling trains ready for a road locomotive to take over, disassembling a train that has been brought in, and generally moving railroad cars around  a process usually known as "switching" (USA) or "shunting" (UK). They do this in classification yards (Great Britain: "marshalling yards"). Switchers may also make short transfer runs and even be the only motive power on branch lines and switching and terminal railroads. The term can also be used to describe the workers operating these engines or engaged in directing shunting operations.  - The Pennsylvania Railroad was an American Class I railroad, founded in 1846. Commonly referred to as the "Pennsy," the PRR was headquartered in Philadelphia, Pennsylvania.  - A railroad car or railcar (American and Canadian English), railway wagon or railway carriage (UK and IUR), also called a train car or train wagon, is a vehicle used for the carrying of cargo or passengers on a rail transport system (a railroad/railway). Such cars, when coupled together and hauled by one or more locomotives, form a train. Alternatively, some passenger cars are self-propelled in which case they may be either single railcars or make up multiple units.  - The ALCO S2 and S4 were 1,000 horsepower ( 746 kW ) diesel electric switchers produced by ALCO and Canadian licensee Montreal Locomotive Works ( MLW ) . Basically , the two locomotives differed only in trucks , with the S - 2 using ALCO 's own `` Blunt '' trucks , and the S - 4 riding on standard AAR type A switcher trucks . Both were powered by ALCO 539 turbocharged , 6 - cylinder diesels . The S - 2 was built between August 1940 and June 1950 , with a total of 1502 completed , while the S - 4 was constructed between June 1949 and August 1957 ( MLW until 1957 ) with total sales of 797 . Canadian production of the S - 4 started more than a year before U S production of the S - 4 . ALCO did not start building the S - 4 until August 1950 . A modified version , the S - 7 , was built by MLW only ; 29 were built between June and August 1957 .  - The American Locomotive Company, often shortened to ALCO, ALCo or Alco, designed, built and sold steam locomotives, diesel-electric locomotives, diesel engines and generators, specialized forgings, high quality steel, armed tanks and automobiles and produced nuclear energy. The American Locomotive Company was formed in 1901 by the merger of Schenectady Locomotive Engine Manufactory of Schenectady, New York with seven smaller locomotive manufacturers.    Given the information, choose the subject and object entities that have the relation of 'manufacturer'.
Answer:
alco s-2 and s-4 , american locomotive company