@Q1: We confirm that the two identified funding agencies are correct. Please
also add the following sentence at the end of the acknowledgement section:
"S. Straupe is grateful to the Dynasty foundation for financial support."

@Q2: Reference check:
The first Author of Ref. 5 should read "Hood C J" instead of "Christina J H";
see http://journals.aps.org/pra/abstract/10.1103/PhysRevA.64.033804

@Q3: Unfortunately, we do not have updated information on Ref [21], possibly
due to a backlog in creating DOI for historical documents. As stated, Ref [22]
may partly help to clarify this.

No further changes found.