What are some recommended mathematical economics books for someone looking to deepen their understanding of economic theory and analysis?

Some recommended mathematical economics books for deepening understanding of economic theory and analysis include "Microeconomic Theory" by Andreu Mas-Colell, Michael D. Whinston, and Jerry R. Green, "Mathematics for Economists" by Carl P. Simon and Lawrence Blume, and "Advanced Macroeconomics" by David Romer.