1. past tense and past participle of refer; mentioned or alluded to something
2. past tense and past participle of refer; directed someone to a source of information or help
3. past tense and past participle of refer; consulted a source for information

Examples

• The teacher referred to the textbook during her lecture.
• She was referred to a specialist by her doctor.
• He referred to his notes before answering the question.
• The article referred to recent studies on climate change.
• The patient was referred to the emergency room.
• I referred to the dictionary to check the spelling.
• The lawyer referred to several legal precedents in his argument.