Additional Reference button appeared in objects in 5.60b5 (see screenshot below).

For some it leads to nonexistant pages:
- Scripts (https://docs.unity3d.com/Manual/class-MonoImporter.html),
- Shaders (https://docs.unity3d.com/Manual/class-ShaderImporter.html),
- Audio (https://docs.unity3d.com/Manual/class-AudioImporter.html),
- Scenes (https://docs.unity3d.com/Manual/class-SceneAsset.html),
- Terrain (https://docs.unity3d.com/Manual/class-TerrainData.html),
- Fonts (https://docs.unity3d.com/Manual/class-TrueTypeFontImporter.html),
- GIParameters (https://docs.unity3d.com/Manual/class-LightmapParameters.html),
- GUISkin (https://docs.unity3d.com/Manual/script-GUISkin.html),
- AnimatorOverrideController (https://docs.unity3d.com/Manual/class-AnimatorOverrideController.html)
- Lightning Data (https://docs.unity3d.com/Manual/class-LightingDataAsset.html)

Tested and works fine with:
- Materials,
- Flare,
- Physics Material,
- Reflection probes,
- Models,
- Avatar Mask,
- Text assets,
- Sprites.

To repro:
1. Open project attached in 5.6.0b5 or add any of listed objects to a new project.
2. Press first reference button.

Actual result: You're navigated to non-existant page in Docs.
Expected result: Expected page is opened.

Regression since 5.6.0b5 (bc8585c89061)
Thu, 19 Jan 2017 13:24:16 GMT
Branch: trunk.

No extra-reference button in 5.6.0b4 (f8c731df0021)
Wed, 11 Jan 2017 17:00:30 GMT
Branch: trunk