When working with Adobe Flash, communicating with various movie clips and swf files can be a pretty stressing.
For nested SWF files, it goes as follows:
1. First SWF (level 0) loads another SWF file into a different level using either loadMovie or loadMovieClip function.
2. The loaded SWF file can then refer to the first SWF by referring to it through "_level0"
For nested movie clips, _root, _parent, this, "instance name of movie clip" can all be used.
_root refers to main timeline
_parent refers to the calling movie clip