17 CFR § 270.8b-21 - Information unknown or not available.
Information required need be given only insofar as it is known or reasonably available to the registrant. If any required information is unknown and not reasonably available to the registrant, either because the obtaining thereof would involve unreasonable effort or expense, or because it rests peculiarly within the knowledge of another person not affiliated with the registrant, the information may be omitted subject to the following conditions:
(a) The registrant shall give such information on the subject as it possesses or can acquire without unreasonable effort or expense, together with the sources thereof.
(b) The registrant shall include a statement either showing that unreasonable effort or expense would be involved or indicating the absence of any affiliation with the person within whose knowledge the information rests and stating the result of a request made to such person for the information.
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