APA
The Earth Works Group, . (1990). 50 Simple Things Kids Can Do To Save the Earth. Nueva York: .
Chicago
The Earth Works Group, . 1990. 50 Simple Things Kids Can Do To Save the Earth. Nueva York: .
Harvard
The Earth Works Group, . (1990). 50 Simple Things Kids Can Do To Save the Earth. Nueva York: .
MLA
The Earth Works Group, . 50 Simple Things Kids Can Do To Save the Earth. Nueva York: . 1990.
