field containing a single message identifier, then the "References:" field will contain the contents of the parent's "In-Reply-To:" field followed by the contents of the parent's "Message-ID:" field (if any). If the parent has none of the "References:", "In-Reply-To:", or "Message-ID:" fields, then the new message will have no "References:" field. Modern email clients then can use the unique message identifiers found in the RFC 822 Message-ID, In-Reply-To: and References: fields of all received email headers to locate the parent and root message in the hierarchy, reconstruct the chain of reply-to actions that created them, and display them as a discussion tree. The purpose of the References: field is to enable reconstruction of the discussion tree even if some replies in it are missing. Advantages Eliminates turn-taking & time constraints Threaded discussions allow readers to quickly grasp the overall structure of a conversation, isolate specific points of conversations nested within the threads, and as a result, post new messages to extend discussions in any existing thread or sub-thread without time constraints. With linear threads on the other hand, once the topic shifts to a new point of discussion, users are: 1) less inclined to make posts to revisit and expand on earlier points of discussion in order to avoid fragmenting the linear conversation similar to what occurs with turn-taking in face-to-face conversations; and/or 2) obligated to make a motion to stay on topic or move to change the topic of discussion. Given this advantage, threaded discussion is most useful for facilitating extended conversations or debates involving complex multi-step tasks (e.g., identify major premises → challenge veracity → share evidence → question accuracy, validity, or relevance of presented evidence) – as often found in newsgroups and complicated email chains – as opposed to simple single-step tasks (e.g., posting or share answers to a simple question). Message targeting Email allows messages to be targeted at particular members of the audience by using the "To" and "CC" lines. However, some message systems do not have this option. As a result, it can be difficult to determine the intended recipient of a particular message. When messages are displayed hierarchically, it is easier to visually identify the author of the previous message. Eliminating list clutter It can be difficult to process, analyze, evaluate, synthesize, and integrate important information when viewing large lists of messages. Grouping messages by thread makes the process of reviewing large numbers