Why Wikipedia doesn't standardize everything
Wikipedia doesn't standardize section headings for citations because the real world doesn't. There are four major style guides that are heavily used in universities, and articles using each one can be found on Wikipedia. Each requires a different name above the list of sources that were used to support content in an academic paper:
Chicago Manual of Style: "Center the title Bibliography about one inch from the top of the page" (used by fine arts and historians)
APA style: "In APA style, the alphabetical list of works cited, which appears at the end of the paper, is titled 'References.'" (used by sociologists and psychologists)
The MLA Style Manual: "Center the title Works Cited about one inch from the top of the page." (used in humanities)
Council of Science Editors: "Center the title References (or Cited References) and then list the works you have cited in the paper; do not include other works you may have read." (used by scientists)
Wikipedia hasn't chosen one over another because nobody wants to be stuck telling the English people that they have to follow scientific conventions, or the history folks that they're required to follow the English manual.
The relative pronoun that is used for restrictive clauses: The car that is red is broken. (The other cars are other colors, and they are not broken.)
The relative pronoun which is used for non-restrictive clauses, such as a description: The car, which is red, is broken. (There's only one car, and I thought you might like to know what color it was painted.)
The relative pronoun who is correctly used in either of these manners, so long as the antecedent is a person. In some situations, such as describing a marginalized group of people, some people may object to the "de-humanization" of the antecedent if that or which are chosen instead of the personhood-affirming who. However, that and which are grammatically correct, and their use in older and formal English is well-established. For example:
John 11:25 (KJV): "Jesus said unto her, 'I am the resurrection, and the life: he that believeth in me, though he were dead, yet shall he live.'"
Luke 16:10 (ERV): "He that is faithful in a very little is faithful also in much: and he that is unrighteous in a very little is unrighteous also in much."
I work for the Wikimedia Foundation in the Community Relations team to answer questions and report problems about some wiki software, especially VisualEditor, but this is my personal account. Edits, statements, or other contributions made from this account are my own, and may not reflect the views of the Foundation. If you want to reach me in an official capacity, then try leaving a message at User talk:Whatamidoing (WMF).