Liang, N.S. and Maruyama, K.  1995.  Interactive effects of CO2 enrichment and drought stress on gas exchange and water-use efficiency in Alnus firma.  Environmental and Experimental Botany 35: 353-361.

Liang, N., Maruyama, K. and Huang, Y.  1995.  Interactions of elevated CO2 and drought stress in gas exchange and water-use efficiency in three temperate deciduous tree species.  Photosynthetica 31: 529-539.