Referrals in Surveys

What is a Referral?
It is a person who has registered on a website by another existing user of that website through a Referral Link. The user who refers a new user receives a percentage of what his referrals earn, increasing the profits.
How to get referrals?
The most viable thing is to invite people to join the survey pages telling them all the advantages of earning extra money and little time invested, it is also viable to publish your referral links through social networks, or some websites recommend you send "mail" to people you know.