Article 1 provides some of the rules for determining whether the CISG applies. Article 1 should be read in connection with articles 2 and 3, which respectively narrow and extend the CISG’s substantive sphere of application. Article 2 identifies sales that are excluded from the CISG’s sphere of application. The exclusions are of three types: those based on the purpose for which the goods were purchased, those based on the type of transaction, and those based on the kinds of goods sold. Article 3 makes clear that the CISG’s sphere of application encompasses some contracts that include acts in addition to the supply of goods. The first sentence of article 4 lists matters as to which the CISG’s provisions prevail over those of domestic law; the formation of contract and the rights and obligations of the parties; the second sentence contains a non-exhaustive list of issues with which, except where the CISG expressly provides otherwise, it is not concerned namely the validity of the contract or any of its provisions or any usage, as well as the effect which the contract may have on the property in the goods sold. The issues referred to in the second part of article 4 were excluded from the CISG because dealing with them would have delayed the conclusion of the CISG. Pursuant to Article 5, the CISG does not deal with liability for death or personal injury caused by the goods to any person, regardless of whether the injured party is the buyer or a third party. Consequently, national law applies to those matters. According to article 6 of the CISG, the parties may exclude the CISG’s application; totally or partially or derogate from its provisions. Thus even if the CISG would otherwise be applicable, in order to decide whether it applies in a particular case one must determine whether the parties have excluded the CISG or derogated from its provisions. According to several courts, opting-out requires a clear expression of intent by the parties. By allowing the parties to exclude the CISG or derogate from its provisions, the drafters affirmed the principle that the primary source of rules for international sales contracts is party autonomy. Thus the drafters clearly acknowledged the CISG’s non-mandatory nature and the central role that party autonomy plays in international commerce specifically, in international sales.