You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
University_of_Chicago

Context:
Undergraduate students are required to take a distribution of courses to satisfy the university's core curriculum known as the Common Core. In 2012-2013, the Core classes at Chicago were limited to 17 students, and are generally led by a full-time professor (as opposed to a teaching assistant). As of the 2013–2014 school year, 15 courses and demonstrated proficiency in a foreign language are required under the Core. Undergraduate courses at the University of Chicago are known for their demanding standards, heavy workload and academic difficulty; according to Uni in the USA, "Among the academic cream of American universities – Harvard, Yale, Princeton, MIT, and the University of Chicago – it is UChicago that can most convincingly claim to provide the most rigorous, intense learning experience."

Question:
What guide states the Univeristy of Chicago is known for their heavy workload and academic difficulty?

Uni in the USA