I've frequently come across questions closed as a duplicate, yet the notification contains no reference to which original question it duplicated, e.g.,
Sometimes there are links to the original, but more frequently the link might be elsewhere on the page, and the alert only contains a listing the users who closed the question as a duplicate.
Users from different backgrounds may not use the same vocabulary (e.g., hash vs. associative array). To allow users who may arrive at a question via a different search query to arrive at their desired content, the link to the original question should always be included in the "question closed" alert. Ideally, this would be bidirectional - since all still exist in the database, the 'parent' question would also contain a section with links to the closed duplicates.