Answer the question on the basis of following passage:
Lenovo India decided to strengthen its diversifying numbers. It decided to tap its referral system. The company asked its employees to recommend candidates and decided to reward those who successfully recommended more women for the same roles.
Today, technology major Infosys for instance, has enhanced the use of technology for the employees' referral process. It has created a portal where employees can view requirements and submit profiles of candidates directly. Employees can then track the status of their referral real-time.
Which of the following is an internal source of recruitment?