a chain of countries that deal exclusively with non-conflict diamonds. By restricting diamond revenues to government-approved sources, the Kimberley Process is neutral towards different governments. Compliance System of warranties The World Diamond Council created a System of Warranties for diamonds that has been endorsed by all KPCS participants. Under this system, all buyers and sellers of both rough and polished diamonds must make the following affirmative statement on all invoices: It is considered a violation of the KPCS to issue a warranty declaration on a sales invoice unless it can be corroborated by warranty invoices received for purchases. Each company trading in diamonds must also keep records of the warranty invoices received and the warranty invoices issued when buying or selling diamonds. This flow of warranties in and out must be audited and reconciled on an annual basis by the company's auditors. In addition, the diamond industry organizations and their members have adopted the following principles of self-regulation: to trade only with companies that include warranty declarations on their invoices; to not buy diamonds from suspect sources or unknown suppliers, or which originate in countries that have not implemented the Kimberley Process Certification Scheme; to not buy diamonds from any sources that, after a legally binding due process system, have been found to have violated government regulations restricting the trade in conflict diamonds; to not buy diamonds in or from any region that is subject to an advisory by a governmental authority indicating that conflict diamonds are emanating from or available for sale in such region, unless diamonds have been exported from such region in compliance with the Kimberley Process Certification Scheme; to not knowingly buy or sell or assist others to buy or sell conflict diamonds; to ensure that all company employees that buy or sell diamonds within the diamond trade are well informed regarding trade resolutions and government regulations restricting the trade in conflict diamonds. Failure to abide by these principles exposes the member to expulsion from industry organizations. Working procedure The working procedure of the KPCS is done by the chair, elected on an annual basis at a plenary meeting. A working group on monitoring, works to ensure that each participant is implementing the scheme correctly. The working group reports to the chair. Other working groups include the technical working group (or working group of diamond experts) which reports on difficulties in implementation and proposes solutions, and