Search Engines. Information Retrieval in Practice

http://www.search-engines-book.com/slides/

7 Ways to Improve Your Website’s or Intranet’s Built-In Search Engine

https://www.nngroup.com/articles/internal-website-search/?utm_source=Alertbox&utm_campaign=2d653fa400-Same_Link_Twice_Improve_Search_Engine_03_14_2016&utm_medium=email&utm_term=0_7f29a2b335-2d653fa400-40018557