The document discusses essential documents for clinical trials. Essential documents are those needed before, during, or after a clinical trial to permit evaluation of the trial conduct and quality of the data produced. They must meet Good Clinical Practice standards and regulatory requirements. There are four sections that classify essential documents: Section 1 provides an introduction; Section 2 covers documents needed before a trial commences; Section 3 covers documents needed during trial conduct; and Section 4 covers documents needed after trial completion or termination.