An assignment of copyright is a transfer of ownership. It must always be in writing and signed by the copyright owner. A licence simply allows another person to use the work without transferring ownership. It does not need to be in writing but it is always advisable to put agreements concerning the use of a work in a written form to avoid disputes as to the terms. Both assignments and licences can be limited by time (for example, for five years only), by territory (e.g. in Australia only) and by the rights to which they apply (e.g. to publish in print form only).