Use reference management software such as Zotero, EndNote, RefMan or Mendeley to format your bibliography correctly. Check your reference formatting one by one! Make sure the essential information is present (reference number, authors, journal names, year, volume, pages or article numbers for journal articles, editor names, publisher, city, publication year for books). Be careful with articles from journals that use article numbers, rather than page numbers as not all reference management software can deal with this automatically.