Original: He was a strong contender for the World Chess Championship from the mid-1930s to the mid-1960s; coming equal third in the World Chess Championship 1948 tournament, and equal second in the 1953 Candidates Tournament.
Simplified: He was a contender for the World Chess Championship from about 1935 to the mid-1960s. He came equal third in the World Chess Championship 1948 tournament, and equal second in the 1953 Candidates Tournament.