At a given degree of induration, massive rocks of sandstone, siltstone, and limestone are the strongest, while shaly rocks with more or less parallel, closely spaced separation surfaces created during sedimentation in thin layers are the weakest. Committee on Underground Coal Mine Safety (1982) Toward Safer Underground Coal Mines Washington, D.C. : National Academy Press, page 32, isbn 978-0-309-03298-8.

It is a one-off; there is nothing else like it.

At first we didn't think it was Annabelle. We doubted and redoubted it. But we're almost certain it was now, although there is a difference in her voice.

All these knives are dull.