Watch out for your own bias! just because you are trying to prove a point in your paper does not eliminate relevant information if you think it disproves your hypothesis
There is bias in almost everything you read. Almost all authors are trying to convince you that their point of view is the best one out there. Depending upon the topic you are researching there will be differing levels of bias. Topics like abortion, religion, animal rights and politics lend themselves to bias. Here are some factors that will determine varying degrees of bias: