The document is an article written by Frederick Marks, a retired purchasing officer, discussing negotiation tactics and how to determine if someone is lying during negotiations. Marks emphasizes the importance of doing research on the opposite party, including their company, tactics, and financial health. He also suggests paying attention to body language, professional language and demeanor, and the use of exaggerated responses or techniques like "good cop, bad cop." Marks advises against falling for artificial deadlines or bluffing tactics and recommends keeping emotions in check during negotiations. He encourages continuous practice and learning to improve negotiation skills.