Sometimes your keywords are too broad, and you find too much material. For books and articles on sybmiosis, sometimes symbiosis is too broad of a search term. You'll need to narrow it to the organism and the relationship:
Fungi bacteria relationships
Mycorrhizae
Host parasite relationships
Or even more specific by including the organisms names:
Clownfish sea anemone
Flatworm green algae
Cattle egrets and buffalo
Broader Terms (BT)
If you are not finding any results, your search could be too narrow. For books and articles relating to a specific species, you may want to try searching just that species alone, or you may want to broaden it to the genus.You may need to narrow or broaden, too, depending on the format you are looking for.
Reef instead of Great Barrier Reef
Mutualism instead of clownfish sea anemone relationship
Related Terms (RT)
Sometimes you can find information by using related searches, like mutualism, instead of symbiosis: