1. Inquire through the publication official website: Many publishers and periodicals will provide the inquiry service of subscription codes in official website. You can search for relevant information in the publication official website.
2. Inquire through the online library: Online libraries, such as the National Library of China, will provide the inquiry service of books and periodicals order numbers, and you can conduct related searches on the websites of these online libraries.
3. Inquire by contacting the publishing house or supplier: If you can't find it online or the information is not enough, you can contact the publishing house or related suppliers to inquire, and they will provide relevant information.