In recent years, a considerable simplification of documentary practices has been achieved. Bills of lading are frequently replaced by non-negotiable documents similar to those which are used for other modes of transport than carriage by sea. These documents are called «sea waybills», «liner waybills», «freight receipts», or variants of such expressions. Non-negotiable documents are quite satisfactory to use except where the buyer wishes to sell the goods in transit by surrendering a paper document to the new buyer. In order to make this possible, the obligation of the seller to provide a bill of lading under CFR and CIF must necessarily be retained. However, when the contracting parties know that the buyer does not contemplate selling the goods in transit, they may specifically agree to relieve the seller from the obligation to provide a bill of lading, or, alternatively, they may use CPT and CIP where there is no requirement to provide a bill of lading.