Distribution of absorbing roots of coffee (Coffea arabica L.) and rubber (Hevea brasiliensis Muell. Arg.) in mixed plantings in two ecological zones of Costa Rica - Gehrke V., Malcolm R. 1938- (M.R. Gehrke V., 1962)
Tesis (Magister Agriculturae)-- Instituto Interamericano de Ciencias Agrícolas de la OEA, 1962