Where is the implementation of the filters in the OpenCV source code?

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Hi.

I would like to see the code for the adaptiveThreshold function, in particular for version 2.4.5, which is what we have installed in our system. I've found the C++ implementation on opencv-2.4.5/modules/imgproc/src/thresh.cpp. The function uses boxFilter and GaussianBlur, but I cannot find their implementation. Only their header definitions. Where is the code for these functions located?

Thanks for any help.