From Burglars in Bucks, by G.D.H. and Margaret Cole:

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[Six dots appear in the middle of a letter one character is writing to another.]

.      .      .      .      .      .

Those dots are Jerry [he writes], coming in.

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"I may accept a poltergeist which breaks crockery, and even, at a pinch, one which doubles up keys in people's pockets, but I will emphatically not accept one which manufactures imitation keys, bends them up so that there is no risk of any one's trying to use them, and substitutes them for the real ones."

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[Writes Everard] "She clutched me and sobbed, 'Oh, Everard!' any number of times; but when I asked what was the matter she only Oh Evararded again."

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"'Racing touts,' said Coulson, ' 'ud be a pretty name for them.' He didn't tell me what an ugly one would have been; but by the shape of his face I could guess."

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Bonus: An offstage character called Lady Doppelganger.