You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
National_Archives_and_Records_Administration

Context:
NARA also maintains the Presidential Library system, a nationwide network of libraries for preserving and making available the documents of U.S. presidents since Herbert Hoover. The Presidential Libraries include:

Question:
What is the system that preserves the documents of US Presidents?

Presidential Library system