See this example properly formatted in the QUT Cite tool.
All ideas that are not your own should be cited (and later referenced).
When you refer to general ideas or just want to acknowledge that an idea came from a secondary resource, then your in-text citation does not require a page number.
Plagiarism is an issue that all students should be aware of (Cope, 2007).
If you read from many sources and have written ideas in your own words, but you know that you learned these ideas from other people, list their names alphabetically in your in-text citation using a semicolon (;) to separate the sources.
Academic writing is more formal and more complicated than informal writing, especially when authors need to consider acknowledging referencing (Cope, 2007; Oshima & Hogue, 1991; Putnis & Petelin, 1999).
For more detail about citing multiple sources at once check the individual styles: