Op. cit. is an abbreviation that is commonly used to refer to a previously cited work in a text. However, there are other ways to indicate this in writing. Some synonyms for op. cit. are "previously mentioned", "already noted", "as previously cited", "as previously mentioned", or "as mentioned earlier". These synonyms serve the same purpose as op. cit. and can be used interchangeably to avoid repetition in writing. Additionally, some academic writing styles have their own conventions for referencing previously cited works, such as using abbreviations or short titles. Regardless of the convention used, it is important to properly reference and acknowledge sources in academic writing.