1. Containment (Wikipedia)
2. Containment 2
3. Containment 3
4. The Long Telegram by George F. Kennan

Truman doctrine

1. Truman doctrine (Wikipedia)
2. Truman doctrine 2
3. Truman doctrine 3

Marshall Plan

• Marshall Plan (Wikipedia)
• Marshall Plan 2
• Marshall Plan 3

Korean War

1. Korean War (Wikipedia)
2. Korean War: an overview
3. Australia in the Korean War

Vietnam War

1. Vietnam War (Wikipedia)
2. Vietnam online
3. Vietnam War

Of course you may use other websites and/or books!