A detailed description of at least one way of carrying out the invention must be given. Since the application is addressed to the person skilled in the art, it is neither necessary nor desirable that details of well-known ancillary features should be given, but the description must disclose any feature essential for carrying out the invention in sufficient detail to render it apparent to the skilled person how to put the invention into practice. A single example may suffice, but where the claims cover a broad field, the application should not usually be regarded as satisfying the requirements of Art. 83 unless the description gives a number of examples or describes alternative embodiments or variations extending over the area protected by the claims. However, regard must be had to the facts of the particular case. There are some instances where even a very broad field is sufficiently exemplified by a limited number of examples or even one example (see also III, 6.3). In these latter cases the application must contain, in addition to the examples, sufficient information to allow the person skilled in the art, using his common general knowledge, to perform the invention over the whole area claimed without undue burden and without needing inventive skill (see T 727/95, OJ 1/2001, 1). If the Examining Division is able to make out a reasoned case that the application lacks sufficient disclosure, the onus of establishing that the invention may be performed and repeated over substantially the whole of the claimed range lies with the applicant (see VI, 2.3).