Rule reference for 2018 March Clarification

[Zepp]

Was hoping if someone could provide the rule reference from the 2018 USA softball rule book which backs up the recently released Rule Clarification (March 2018) that is provided below?

Q. Can an EP run for anyone in the line-up?
A. An EP can be a pinch runner for anyone. However our Re-entry Rule would still be in effect. The EP would be considered a substitute for the person they are running so the person who they run for and the EP running will have one more reentry. The EP is now tied to that person and can only pinch run for that person. Once they have used up their re-entry they still may bat and play defense but can no longer be a pinch runner.