Upon consideration, and taking account of the jurisprudence of the Court, the Chamber finds that there are no grounds to interpret the declaration in question as a unilateral act with legal implications in regard to the dispute. The Judgment then goes on to consider the principles of delimitation approved by the Legal Sub-commission which, according to Burkina Faso, Mali agreed should be taken into consideration in delimiting the frontier in the disputed area. Having weighed the arguments of the Parties, the Chamber concludes that, since it has to determine the frontier line on the basis of international law, it is of little significance whether Mali’s approach may be construed to reflect a specific position towards, or indeed to signify acquiescence in, the principles held by the Legal Sub-Commission to be applicable to the resolution of the dispute. If those principles are applicable as elements of law, they remain so whatever Mali’s attitude. The situation would only be otherwise if the two Parties had asked the Chamber to take account of them or had given them a special place in the Special Agreement as “rules expressly recognized by the contesting States” (Art. 38, para. 1 (a) of the Statute), neither of which was the case. The Chamber disposes of a further preliminary question, concerning its powers in the matter of fixing the tripoint which forms the easternmost point of the frontier between the Parties. Their views on this question conflict. Mali claims that the determination of the tripoint Niger-Mali-Burkina Faso cannot be effected by the two Parties without Niger’s agreement, and cannot be determined by the Chamber either and Burkina Faso considers that the Chamber must, pursuant to the Special Agreement, reach a decision on the position of the tripoint. As for its jurisdiction in this matter, the Chamber finds it to be clear from the wording of the Special Agreement that the common intention of the Parties, was that it should indicate the frontier line throughout the whole of the disputed area. In addition, it considers that its jurisdiction is not restricted simply because the end-point of the frontier lies on the frontier of a thud State not a party to the proceedings. The rights of the neighbouring State, Niger, are in any event safeguarded by the operation of Article 59 of the Statute of the Court. Regarding the question whether considerations relating to the need to safeguard the interests of the third State concerned would require the Chamber to refrain from exercising its jurisdiction to determine the whole course of the line, this presupposes, according to the Chamber, that the legal interests of that State would not only be affected by its decision, but would form the very subject-matter of that decision. This is not so in this case, and the Chamber is accordingly required to determine how far the frontier inherited from the colonizing State extends. This is, for the Chamber, not a matter so much of defining a tripoint as of indicating where the easternmost point of the frontier lies, the point where the frontier ceases to divide the territories of Burkina Faso and the Republic of Mali. The Parties have relied upon different types of evidence to give support to their arguments. They have referred to legislative and regulative texts or administrative documents, of which the basic document is the French law of 4 September 1947 “for the reestablishment of the territory of Upper Volta”, providing that the boundaries of the re-established territory were to be “those of the former colony of Upper Volta on 5 September 1932”. At the time of independence in 1960, those boundaries were the same as those which had existed on 5 September 1932. 1932. However, the texts and documents produced in evidence contain no complete description of the course of the boundary between French Sudan and Upper Volta during the two periods when these colonies coexisted (1919-1932 and 1947-1960). They are limited in scope, and their legal force or the correct interpretation of them are matters of dispute between the Parties. The two States have also produced an abundant and varied collection of cartographic materials, and have discussed in considerable detail the question of the probative force of the maps and the respective legal force of the various kinds of evidence. The Chamber notes that, in frontier delimitations, maps merely constitute information, and never constitute territorial titles in themselves alone. They are merely extrinsic evidence which may be used, along with other evidence, to establish the real facts. Their value depends on technical reliability and their neutrality in relation to the dispute and the parties to that dispute they cannot effect any reversal of the onus of proof. When considering the maps produced in this case, the Chamber notes that not one of the maps available to it can provide a direct official illustration of the words contained in four essential texts even though it was clear from their wording that two of those texts were intended to be accompanied by maps. Although the Chamber has been presented with a considerable body of maps, sketches and drawings for a region that is nevertheless described as partly unknown, no indisputable frontier line can be discerned from these documents. Particular vigilance emphasizes is therefore required in examining the file of maps. Among the evidence to be taken into consideration, the parties invoke the “colonial effectivities”, in other words, the conduct of the administrative authorities as proof of the effective exercise of territorial jurisdiction in the region during the colonial period. The role played by such effectivities is complex, and the Chamber has to make a careful evaluation of their legal force in each particular instance.