To eliminate competition and thereby secure higher prices, firms producing a specific product can come together and make monopoly agreements. These are called as industrial combinations. When all the firms merge into one organisation, such a monopoly takes the form of a trust.The firms sustain their individual identity and yet enter into monopoly agreements such combinations are called as trade associations, cartels, pools and holding companies. A pool is deemed a loose combination to sustain a particular higher price level of a commodity. A cartel is based on agreements to restrict output to get high prices. A holding company secures monopolistic control over some firms by holding a majority of shares in them.