The key to avoiding inadvertent plagiarism is learning how to correctly paraphrase. Harvard Graduate School of Education's well-developed tutorial on paraphrasing does not take long to complete. The tutorial references APA citation style, but the lessons on paraphrasing are relevant to all disciplines.
A free certification test provided by Indiana University at Bloomington's School of Education. Two version of the certification test are offered: one for undergraduates and one for graduate students. Instructors can easily validate certificates earned by students through this system.
Doing Honest Work in College by 
Stop Plagiarism by 
The Complete Guide to Referencing and Avoiding Plagarism by 
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