Products Laboratory (U.S.), F., Keller, E., Kingsbury, R., & Fahey, D. (1965). Neutral sulfite semichemical pulping of guaba (Inga vera), yagrumo hembra (Cecropia peltata), and eucalyptus (Eucalyptus robusta) from Puerto Rico. : Madison, Wis. : U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory.