As mentioned previously, there are several synonyms for the phrase "as mentioned before". Some of these synonyms include "as stated earlier", "as previously noted", "as previously mentioned", and "as said earlier". All of these phrases convey the same message and are used to indicate that the topic being discussed has been talked about before. Using these synonyms can help add variety to your writing and prevent repetitive or monotonous language. It also ensures that your readers are able to follow your train of thought and understand the context of your writing.