Retail agreements can also be considered invitations to treat if there is simply not enough information in the initial statement for it to constitute an offer. In "Partridge v Crittenden" [1968] 1 WLR 1204 the defendant had placed an advertisement indicating that he had certain birds for sale, giving a price but no information about quantities. He was arrested under the Protection of Birds Act 1954 for 'offering such birds for sale'; it was ruled that since the advertisement did not specify the number of birds he had it could not constitute an offer; if it did he could have been legally bound to provide more birds than he possessed. The same principle was applied for catalogues in "Grainger v Gough" [1896] AC 325, when it was ruled that posting catalogues of items for sale to people did not constitute an offer since there was insufficient detail. An offer can be rejected by the offeree(s). The conduct of an offeree(s) has led to the non-existence of the offer. See  When an offer is stated to be open for a specific length of time, the offer automatically terminates when it exceeds the time limit. See:       A writes to B offering to sell certain property at a stated price. B writes to A offering to buy the same property at the same price. The letters cross in the post. Is there (a) an offer and acceptance, (b) a contract? In this case, It is assumed that "where offers cross there was no binding contract". Because B's acceptance was not communicated to A. Therefore, there was no contract what so ever. Revocation can be made by the offeror only before acceptance is made. Also the revocation must be communicated to the offeree(s).Unless and until the revocation is communicated, it is ineffective. See:  If the terms of the contract are uncertain or incomplete, the parties cannot have reached an agreement in the eyes of the law. An agreement to agree does not constitute a contract, and an inability to agree on key issues, which may include such things as price or safety, may cause the entire contract to fail. However, a court will attempt to give effect to commercial contracts where possible, by construing a reasonable construction of the contract ("Hillas and Co Ltd v Arcos Ltd"). Courts may also look to external standards, which are either mentioned explicitly in the contract or implied by common practice in a certain field. In addition, the court may also imply a term; if price is excluded, the court may imply a reasonable price, with the exception of land, and second-hand goods, which are unique.