Rule 28(b) of the Rules of Civil Procedure for the District Courts of the United States provides that depositions may be taken in foreign countries by any of the following four methods:

(a) Pursuant to any applicable treaty or convention, or

(b) Pursuant to a letter of request (whether or not captioned a letter rogatory), or

(c) On notice before a person authorized to administer oaths in the place in which the examination is held, either by the law thereof or by the law of the United States. Notarizing officials as defined by 22 CFR 92.1 are so authorized by the law of the United States, or

(d) Before a person commissioned by the court, and a person so commissioned shall have the power by virtue of the commission to administer any necessary oath and take testimony.