international tribunal is completely at liberty to deny or to give probative weight to depositions or affidavits, as it may to other evidence and even where the affiant has testified as to matters of direct knowledge, the tribunal is not bound to consider this as conclusive evidence. In the Tacna-Arica Arbitration, President Coolidge, disposing of the charge that Chile had expelled Peruvians from the disputed area in 340 cases, held that ex parte affidavits, few of which made out a sufficient prima facie case, were "too unsubstantial a founda¬tion upon which to establish such a charge." (Opinion and Award of the Arbitrator, p.30. See also the McCardy case, U. S. Mexico, Opinions, 1929, pp. 140,141.) 11. Additional examples of evidentiary materials admitted by international tribunals are: letters; current price lists; consular certificates as to the contents of documents; procla¬mations, maps and photographs (cf. Ralston, Law and Procedures of International Tribunals, pp. 215 ff. 1 Wigmore, Evidence pp. 155. The United States Section of the Agrarian Claims Commission regularly approved of the use of photographs of the property in issue, where properly identified). All such ma¬terials should bo appropriately identified and authenticated. The essential principle of the authentication of documents at common law is equally applicable in international judicial pro¬ceedings; there must be some evidence of their genuineness (Sandifer, op.cit. p.190). In the case of public or official documents, authentication would require certification to the authentic character of the original, (or copy, as the case may be) by the officer charged with their custody. His signature and seal must then be certified by a responsible governmental official, who by reason of his office, is in a position to identify them. (For further details, see Sandifer, op.cit. p.191). It is well-settled, however, that no necessity exists for formally proving the genuineness of printed matter purport¬ing to be published by the Government. Official publications of laws, statutes, judicial decisions and miscellaneous public documents may be admitted or referred to without being formally proved (See Wigmore, Evidence 579, and Sandifer, op.cit., p.198 and authorities cited). Publications such as Senate Document No. 47, 79th Congress, 1st Session, dealing with "Atrocities and other Conditions in Concentration Camps in Germany", would appear to fall within this category. Similarly, records kept by public officials in the regular course of their duties which permitted them to obtain information bearing upon the acts in issue in a given case are admissible. In some cases tribunals