The two sources of restricted entry under monopoly are as follows:
1) Government Licensing: It means that before a firm can enter an industry, it needs to take permission from the government. Licensing is used to ensure minimum standards of competency. By not granting licenses to new firms, government aims to assure that only one firm operates in the market.
2) Patent rights: Certain big private companies are engaged in research and development activities. At times, they come up with new technologies. As a reward for their risk and investment in research, government grant them patent right. The period for which patent rights is known as patent life.
