@article {1573, title = {A conservation asssessment of limestone hills in the Kinta Valley}, number = {MNS Project 90(1)}, year = {1991}, pages = {210}, author = {Malayan Nature Society} } @article {44, title = {Notes on the non-marine molluscs of the island of Borneo 2. The genus Opisthostoma (Gastropoda Prosobranchia: Diplommatinidae), part 2}, journal = {Basteria}, volume = {55}, year = {1991}, pages = {139-163}, chapter = {139}, author = {J.J. Vermeulen} }