The requirement that in order to secure certain intellectual property rights, some public deposit of the subject matter of the intellectual property must be made. In the context of copyright, the requirement that copies of works be deposited with copyright libraries (e.g., the National Library, the Library of Congress, etc.) was prevalent before Berne Convention abolished most copyright formalities—many publishers still make such deposits, especially in the United States where they are necessary for Copyright Registration (which increases the remedies available to a copyright holder in infringement cases). Depository requirements also exist with respect to plant patents and where patents are based on the use of micro-organisms, either naturally occurring or man-made, and arise because of the ‘enablement’ requirement in patent laws. The latter deposit requirements are usually fulfilled by placing samples on deposit with an Escrow Agent. Examples of materials subject to such a deposit requirement are antibiotic expressing microbes or cell-lines of hybridomas that express specific antibodies. See Budapest Treaty on International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedure.