The study of pressure groups usually a twentieth century development. One thing is certain and rightly established by the academic discoveries that in modern society there are different types of groups, quite distinct from political parties that continue influencing the political system. Robert H. Salisbury describes that "pressure groups is only more pejorative but perhaps more familiar a term for interest group". This difference is also supported by the Encyclopaedia of Social Sciences where the pressure group is defined by its techniques and an interest group by its objectives but whenever an interest group adopts the technique of pressure for the fullfilment of its objectives then it converts into "pressure groups". "Pressure groups forge different strategies to protect and promote their interests, taking into consideration the temperament of the people and legal and constitutional framework of the nation".