The Early Years of Paul Keres

Chess24 was launched in 2014 with offices in Hamburg and Gibraltar and advertises itself as the best destination for watching top chess tournaments and enjoying the highest quality chess content online. They have a very nice 4-part series on Paul Keres that you should check out. 

Part I: Prince without a Crown (1916-36) 
Part II: A new chess superstar (1936-37) 
Part III: AVRO 1938: Rightful challenger 
Part IV: The War Years