question: What is the significance of Principia Mathematica currently ?
answer: regarded as one of the most important works in mathematical logic of the 20th century
turker_answer: The significance of Principia Mathematica currently is regarded as one of the most important works in mathematical logic of the 20th century .
rule-based: The significance of Principia Mathematica currently is regarded as one of the most important works in mathematical logic of the 20th century .