Large Language Models (LLMs) are increasingly used for citation retrieval, yet their bibliographic outputs often contain hallucinated or inconsistent metadata. This paper examines whether structured prompting improves citation reliability compared with traditional API-based retrieval. We implement a three-stage BibTeX-fetching pipeline: a baseline Crossref resolver, a standard GPT prompting method, and a customized verification-guided GPT configuration. Across heterogeneous reference inputs, we evaluate retrieval coverage, field completeness, and metadata accuracy against Crossref ground truth. Results show that prompting improves coverage and completeness. Our findings highlight the importance of prompt design for building reliable, LLM-driven bibliographic retrieval systems.