A vertical search engine is a professional search engine for a certain industry. It integrates certain types of specialized information in web resources once, extracts the required data by targeted subfields, processes them, and returns them to the user in some form. Based on the above definition, which of the following applications are most relevant to vertical search engines? ['Buy shoes online at a shopping site.', 'Check CCTV website for weather.', 'Search your favorite songs with Baidu Music.', "Check the library's collections on the library website."]