2. Plans of economic and financial co-operation between a State attacked and the different States assisting it; and shall communicate these plans to the Members of the League. Article 16b. [Sidenote: Article 13 of the Protocol, with slight changes.] In view of the contingent military, naval and air sanctions provided for by Article 16, the Council shall be entitled to receive undertakings from Members of the League determining in advance the military, naval and air forces which they would be able to bring into action immediately to ensure the fulfilment of the obligations in regard to sanctions which result from the Covenant. {279} Furthermore, as soon as the Council has called upon the Members of the League to apply sanctions, as provided in Article 15d, the said Members of the League may, in accordance with any agreements which they may previously have concluded, bring to the assistance of a particular State, which is the victim of aggression, their military, naval and air forces. The agreements mentioned in the preceding paragraph shall be registered and published by the Secretariat. They shall remain open to all Members of the League which may desire to accede thereto. Article 17. [Sidenote: Article 17 of the Covenant, with verbal changes.] In the event of a dispute between a Member of the League and a State which is not a Member of the League, or between States not Members of the League, the State or States not Members of the League shall be invited to accept the obligations of membership in the League for the purposes of such dispute, upon such conditions as the Council may deem just. If such invitation is accepted, the provisions of the Covenant shall be applied with such modifications as may be deemed necessary by the Council. Upon such invitation being given, the Council shall immediately institute an inquiry into the circumstances of the dispute and recommend such action as may seem best and most effectual in the circumstances. If a State so invited shall refuse to accept the obligations of membership in the League for the purposes of such dispute and shall resort to war against a Member of the League, the provisions of Article 16 shall be applicable as against the State taking such action. If both parties to the dispute when so invited refuse to accept the obligations of membership in the League for the purposes of such dispute, the Council may take such measures and make such recommendations as will prevent hostilities and will result in the settlement of the dispute. Article 17a. [Sidenote: Article 15 of the Protocol, with verbal changes.]