What AHD, D.J., Johns and K.K. stand for?

[gusest]

The words in my dictionary are given their pronunciations in ways of AHD, D.J., Johns and K.K. respectively. But I don't know what AHD, D.J., Johns and K.K. stand for. Please help me.

gusest

[Mister Micawber]

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AHD = American Heritage Dictionary

Where are you? I suspect that DJ and KK are Japanese/English dictionaries. Johns has me stumped.
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_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mister Micawber