<li><a href="https://stackoverflow.com">StackOverlow</a> code was used for functions:
            <ul dir="auto">
              <li><a href="https://stackoverflow.com/a/10372280/387194">fworker</a>,</li>
              <li><a href="https://stackoverflow.com/a/27282907/387194">flatten</a>,</li>
              <li><a href="https://stackoverflow.com/a/4331218/387194">allPossibleCases</a>.</li>