The FLink tool has been retired. Please consider using the Entrez Utility (EUtilties) to create your own scripting solution https://www.ncbi.nlm.nih.gov/books/NBK25501.
To cite FLink, please use the following format, based on Citing Medicine: The NLM Style Guide for Authors, Editors, and Publishers (2nd ed., 2007), Chapter 24: Databases/Retrieval Systems on the Internet.