A pointer to an external aid presented by the instrument such as a text card, image, audio, or audiovisual aid. Typically a URN. Use type attribute to describe the type of external aid provided. Example of terms to use would include: imageOnly audioOnly audioVisual multiMedia. ExternalAid will be available each time the control construct is invoked. Care should be taken when placing an ExternalAid in RepeatWhile, RepeatUntil and Loop constructs as it will recur each time the conditional statement is checked. This does not include interviewer instructions, which are handled separately.