"Searching for patents on a particular topic is usually difficult and time-consuming. This can be because the particular approach requested is poorly catered for by the classification, and also because of the sheer volume of material, which has to be looked through.

If the search is meant to gather as much information as possible on a particular subject for all periods and perhaps, for all countries, it is best to begin with the most recent patents and to work back in time. This is because recent patents may refer to earlier patents in their search reports and/or in the preliminary discussion within the description. These may refer to earlier, relevant patents that would, perhaps, never be identified."