APA

Helzer H., . (1975). The psychic world of plants. New York: Pyramid books.

Chicago

Helzer Hans, . 1975. The psychic world of plants. New York: Pyramid books.

Harvard

Helzer H., . (1975). The psychic world of plants. New York: Pyramid books.

MLA

Helzer Hans, . The psychic world of plants. New York: Pyramid books. 1975.