I'm going through some reference books to see what Wikipedia is lacking. Below are topics from the Encyclopedia of the 20th Century (published, I believe, by Facts on File), that do not appear in Wikipedia. This is a single volume work, and Wikipedia is pretty good on more recent topics, so there shouldn't be all that many, but I guess there are.
A
edit- Abdali
- Kjeld Abell
- Abemana Atoll
- Lascalles Abercrombie
- Achinese Rebellion 1953 - 1959
- John Bertram Adams
- Roger Adams
- Samuel A. Adams
- Halide Edib Adıvar
- Samuel Adler (artist)
- Count Alois Lexa von Aehrenthal
- Afghan Civil War (1928-1929)
- Aleksandr Nikolaevich Afinogenov
- Uno Ahren
- Airflow Chrysler
- Ajdabiyah aka Agedabia
- Wallace Allen Akers
- Vassily Aksynov
- Albanian Uprisings (1910, 1932, 1935, 1937)
- Anni Albers
- John G. Alden
- Algerian-Moroccan War (1963-1964)
- Al-Kuneitra
- Fran Allison
- All Power to the Soviets
- All-Russian Directory
- Al-Mechili
- Edoardo Amaldi
- Giorgio Amendola
- Alexander Amfiteatrov
- Ancre River
- Bishop Agnelius Andrew
- Andrei Andreyev
- Jerzy Andrzjewski
- Odysseus Anghelis
- Eberhard Anheuser
- Vladimir Aleksandrovich Antonov-Oveseyenko
- Joseph Appiah
- Aleksei Nikolaevich Arbuzov
- Arcos Raid
- Argentine Revolt (1951, 1955, 1962-63)
- Roberto Emilio Arias
- Armenian Massacre of 1909
- Jean-Paul Aron
- Gerald Arpino
- Karl Albert Ludwig Aschoff
- Nikolai Aseyev
- Ana Aslan
- Carl Auböck
- Evangelos Averoff-Tositsas
B
edit- David Bache
- Paolo Baffi
- Bailey v. Drexel Furniture Co.
- Faith Baldwin
- Frank B. Bane
- Harold Chamberlain Banks
- Joseph Bancroft
- George Barger
- Oscar Barnack
- Joseph Edward Barnard or Joseph Barnard
- Salo Whittmayer Baron
- Alfred Hamilton Barr, Jr.
- Barrow Canyon
- Philip Barry
- Paul Doughty Bartlett or Paul Bartlett
- Jules Bastin
- Leslie Fleetwood Bates or Leslie Bates
- Riccardo Bauer
- Sir Frederick Charles Bawden or Frederick Charles Bawden, Frederick Bawden
- Willi Baumeister
- Sir William Maddock Bayliss or William Maddock Bayliss, William Bayliss
- David Bazelon
- William Baziotes
- Beck case concering David Beck of the Teamsters Union, NOT Adolph Beck
- Demyan Bedny
- Sir George Thomas Beilby or George Thomas Beilby, George Beilby
- Bellau Wood
- Pedro Gerardo Beltran Espantoso
- Lauretta Bender
- Alfred Bensch
- D. C. T. Bennett
- Ward Bennett
- Roloff Beny
- Aksel Ivanovich Berg or Aksel Berg
- Herbert Berghof
- Berkshire Festival
- Flaminio Bertoni
- Nuccio Bertone
- Peter Bessell
- Herbert Beuve-Mery
- Alexander Mikhailovich Bezobrazov
- Billy the Kid (ballet)
- Ronald Eric Bishop, or Ronald Bishop
- Blachownia
- Misha Black
- Black Mask School(could probably be mentioned in and redirected to Black Mask)
- Black Patch War
- Antonoli Blagonravov
- Colin Blakely
- Max Ernst August Bodenstein
- Boer Uprising (1914-1915)
- Nikolai Nikolaevich Bogoliubov
- Bolivian Guerilla War (1966-1967)
- Bolivian National Revolution
- Ilya Bolotowsky
- Bertram Borden Boltwood or Bertram Boltwood
- George F. Bond
- James Frederick Bonner or James Bonner
- Bonn Pact
- Lucrezia Bori
- Michel Boue
- Pierre Boulanger
- Mark Boxer or Marc Boxer
- William Clouser Boyd or William C. Boyd
- Jean Louis Auguste Brachet
- Jenny Bradley
- John Grist Brainerd or John Brainerd
- Francis William Rogers Brambell or Francis Brambell
- Brandt Report
- Carl Henry Brans
- Wiley Austin Branton or Wiley Branton
- John Randolph Bray or John R. Bray