MIDAS Dataset Not Available

The link to the [MIDAS dataset](http://www.insight-journal.org/midas/community/view/21) is currently broken. Several papers mention this dataset, and all of them point to this same link, which has been down since at least November of last year and remains non-functional.

Start by verifying the MIDAS dataset URL reported in the issue and identifying where InsightJournal or its papers reference it. Research whether an authoritative replacement exists; done means the affected reference points to a working, appropriate dataset location and the link has been verified.

索引モデルが issue の本文から書いたものです。