How to spot hydra in the sky. 

 - Singapore:  BBC Studios, UK Publishing,  2022. 
 - p. 82. 
 - BBC Earth: Your Productive Brain.  No. 03.  Vol. 14, .
<br/><br/><label>Subjects--Topical Terms: </label>
<br/><br/><label>Dewey Class. No.: </label>BBC Earth H8301 2022