In August 1999, postal authorities also four designs in se-tenant form to honor the World Wide Fund for Nature.   The issue included a souvenir sheet of eight released in both perforate and imperforate form. Although the Scott catalog lists the series as collectible as a se-tenant block, both Yvert and Tellier and Stanley Gibbons consider the se-tenant values as separate stamps, listing them individually with catalog notations that they were released as a composite block.   In recognition of those listings and the collecting style of any number of philatelists, we therefore add the additional designs to the collectibles of this series.