[1] https://www.hnsearch.com/search#request/submissions&q=%22hac...
[2] https://www.hnsearch.com/search#request/submissions&q=show+%...
[3] https://www.hnsearch.com/search#request/submissions&q=%22sho...
Edit: [2] finds this 'Show HN: Hacker News for "Hacker News for 'X'"': https://news.ycombinator.com/item?id=5436841.
Edit 2: Improved the search queries.