[1] Resource Hints () <https://w3c.github.io/resource-hints/#h-hint-probability-pr-attribute>
[2] Removed the `pr` attribute definition and examples (yoavweiss著, ) <https://github.com/w3c/resource-hints/commit/9769790bdc00d7d7f747cc26f60a0131f851d1db>
[3] Removed the `pr` attribute definition and examples by yoavweiss · Pull Request #76 · w3c/resource-hints () <https://github.com/w3c/resource-hints/pull/76>