The term ‘source’ articulates what the law is and where it can be found. In developed legal systems, sources may be readily identifiable in the form of legislation and judicial decisions. However, sources of international law are not as explicit and accessible as those of municipal law, nor is the machinery for their identification comparable to municipal law. The concept of ‘sources of international law’ faces many conceptual difficulties. Jurists of international law do not agree on the very concept of “source.” They evaluate it from their doctrinal philosophy regarding the basis of international legal obligations. A distinction has also been made between formal sources and material sources of international law. From formal sources, the law derives its authority or sanction, and from material sources, the law derives its content or subject matter.