http://blogs.bu.edu/guidedhistory/historians-craft/katherine-ruiz-diaz/ - This explanation of serfdom in Russia comes from Boston University. Katherine E. Ruiz-Díaz writes about the historical foundation of serfdom - particularly based in agriculture - as well as religious tendencies, the treatment of women in this society, and their eventual liberation.
http://www.newworldencyclopedia.org/entry/Scramble_for_Africa - The New World Encyclopedia defines the Scramble for Africa: what caused and justified the scramble to the Europeans, the various clashes amongst European imperial powers, and the Suez Canal, among other topics.
https://www.youtube.com/watch?v=AHemd90ZdsU – This is a very brief summary of the origins of the term “Manifest Destiny” from The History Channel. It discusses where the phrase came from as well as the controversy it stirred at its inception as well as still in modern times.
https://youtu.be/VA4GlIjubcs?t=59s –The Armchair Historian covers the basics of the Scramble for Africa, including the lead-up to the imperial scramble and how the territory was divided amongst the European powers. (Beginning at 59s)