text: import React, { Component } from 'react';
  
  export default class Sources extends Component {
      render() {
          return (
              <div id="references">
                  <b>REFERENCES</b>
                  <p id="ref-1">
                      [<a href="#uref-1">i</a>]&nbsp;
                      Neipp, Cristian & Hernández, A & Rodes-Roca, Jose & Márquez, 
                      Andrés & Beléndez, T & Beléndez, Augusto. (2003). An analysis 
                      of the classical Doppler effect. European Journal of Physics. 
                      24. 497. 10.1088/0143-0807/24/5/306.
                  </p>
                  <p id="ref-2">
                      [<a href="#uref-2">ii</a>]&nbsp;
                      <a href="https://www.physicsclassroom.com/class/waves/Lesson-3/The-Doppler-Effect">
                          Henderson, Tom. “Physics Tutorial: The Doppler Effect.” The Physics 
                          Classroom, 2016, www.physicsclassroom.com/class/waves/Lesson-3/The-Doppler-Effect
                      </a>
                  </p>
                  <p id="ref-3">
                      [<a href="#uref-3">iii</a>]&nbsp;
                      <a href="https://web.archive.org/web/20170914003837/www.einstein-online.info/spotlights/doppler">
                          Possel, Markus. “Waves, Motion and Frequency: the Doppler Effect.” Waves, 
                          Motion and Frequency: the Doppler Effect - Einstein Online, 
                          web.archive.org/web/20170914003837/www.einstein-online.info/spotlights/doppler
                      </a>
                  </p>
                  <p id="ref-4">
                      [<a href="#uref-4">iv</a>]&nbsp;
                      <a href="https://www.physicsworld.com/a/doppler-shift-is-seen-in-reverse/">
                          Physics World. “Doppler Shift Is Seen in Reverse.” Physics World, 25 Aug. 
                          2017, physicsworld.com/a/doppler-shift-is-seen-in-reverse/
                      </a>
                  </p>
                  <p id="ref-5">
                      [<a href="#uref-5">v</a>]&nbsp;
                      Richard L. Kremer, "The Search for Christian Doppler. Alec Eden ," Isis 85, no. 4 (Dec., 1994): 708-709.
                  </p>
                  <p id="ref-6">
                      [<a href="#uref-6">vi</a>]&nbsp;
                      <a href="https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-microgravity-58.html">
                          Dunbar, Brian. “What Is Microgravity?” NASA, NASA, 16 June 2015, www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-microgravity-58.html
                      </a>
                  </p>
                  <p id="ref-7">
                      [<a href="#uref-7">vii</a>]&nbsp;
                      <a href="https://www.qrg.northwestern.edu/projects/vss/docs/space-environment/zoom-energy.html">
                          Education, Northwest. “Is There Energy in Space?” Is There Energy in Space?, www.qrg.northwestern.edu/projects/vss/docs/space-environment/zoom-energy.html
                      </a>
                  </p>
                  <p id="ref-8">
                      [<a href="#uref-8">viii</a>]&nbsp;
                      <a href="https://pumas.nasa.gov/files/06_09_05_1.pdf">
                          Edberg, Stephen J. “What the Doppler Effect Tells Us About Distant Stars & Planets.” What the Doppler Effect Tells Us About Distant Stars & Planets, 24 Oct. 2005, pumas.nasa.gov/files/06_09_05_1.pdf
                      </a>
                  </p>
            </div>
          )
      }
  }