Seniors' papers can't be referenced, because schools can check the duplicate to find the reference library, undergraduates can use pmlc to check the reference library of undergraduates' papers, which is the discussion library of undergraduates, and postgraduates can use 5. 1 or tmlc to check the reference library of academic papers, which is the discussion library of postgraduates. You can refer to the seniors. You can refer to some books because the school can't find them. In addition, the same session does not check the weight!