1. Oxford Advanced Learner’s Dictionary online. Anxiety meaning. https://www.oxfordlearnersdictionaries.com/definition/english/anxiety
2. Anxiety definition. https://en.wikipedia.org/wiki/Anxiety
3. Pittman, C.M., Karle, E.M.: Rewire Your Anxious Brain: How to Use the Neuroscience of Fear to End Anxiety, Panic and Worry. New Harbinger Publications, Oakland (2015)
4. Sapolsky, R.M.: Why Zebras Don’t Get Ulcers. St Martins Griffin, New York (2004)
5. Le Doux, J.: Anxious: Using the Brain to Understand and Treat Fear and Anxiety. Penguin, New York (2016)