Levoamphetamine increases concentration for 2 hours.
Guajiboan -LRB- also Guahiban , Wahivoan , Guahiboan -RRB- is a language family spoken in the Orinoco River region in eastern Colombia and southwestern Venezuela , which is a savannah-like area known in Colombia as the Llanos .. Colombia. Colombia. Venezuela. Venezuela. language family. language family. Orinoco. Orinoco. savannah. savannah. Llanos. Los Llanos, Venezuela