Paper duplication checking system is a common tool in academic circles, which is used to detect plagiarism and repetition in academic papers. Here are some recommended and easy-to-use paper double-check systems:

1.Turnitin: Turnitin is one of the largest academic duplicate checking systems in the world, which is widely used in academic circles and educational institutions. It can detect the similarity of texts and provide detailed reports to help students and teachers find plagiarism and repetition.

2.Grammarly: Grammarly is a powerful grammar and spelling checking tool, and it also has the function of double checking. It can detect similar contents in texts and provide suggestions and modifications to help users improve their writing quality.

3.Copyscape: Copyscape is a duplicate checking tool specially used to detect the content of web pages. It can help users find out whether there is something similar to their own articles on the Internet and avoid plagiarism and infringement.

4.Plagscan: Plagscan is a professional academic duplicate checking system, which is widely used in academia and research institutions. It can detect the similarity of texts and provide detailed reports to help users find plagiarism and duplication.

5.Viper:Viper is a free online duplicate checking tool, which can help users detect the similarity of texts. It supports a variety of file formats, including Word, PDF and Web pages, and is easy to use and accurate.

These paper duplicate checking systems have different characteristics and advantages, so you can choose the system that suits you according to your personal needs. No matter which system you choose, you should pay attention to protecting intellectual property rights, abide by academic ethics, and avoid plagiarism and infringement.