; (3) the most common types of virtual currencies used by individuals involved in the distribution of opioids through illicit marketplaces on the dark web; (4) an assessment of the capacity to investigate the use of virtual currencies in the distribution of opioids through illicit marketplaces on the dark web, including— (A) efforts to assist financial institutions in detecting, identifying, and reporting suspicious activity and money laundering; (B) efforts to obtain financial records and other documents from virtual currency operators and exchanges; (C) training and guidance to Federal, State, Tribal, and local law enforcement agencies and prosecutors; and (D) coordination and collaboration with international partners; and (5) recommendations for additional congressional or legislative action that would improve the efforts of Federal agencies to detect, disrupt, and dismantle illicit marketplaces on the dark web, including efforts to identify individuals using virtual currencies in the distribution of opioids through illicit marketplaces on the dark web. 7. Five-year update It is the sense of Congress that, not less frequently than once every 5 years, Congress should evaluate and, if necessary, update the definition of the term dark web in section 401(i) of the Controlled Substances Act ( 21 U.S.C. 841(i) ), as added by section 4 of this Act. 8. Severability If any portion of this Act, or the amendments made by this Act, or the application thereof to any person or circumstance is held invalid, the remainder of this Act and the amendments made by this Act, and the application of this Act or the amendments made by this Act to other persons not similarly situated or to other circumstances shall not be affected by the invalidation.