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:
Czech_language

Context:
Czech has one of the most phonemic orthographies of all European languages. Its thirty-one graphemes represent thirty sounds (in most dialects, i and y have the same sound), and it contains only one digraph: ch, which follows h in the alphabet. As a result, some of its characters have been used by phonologists to denote corresponding sounds in other languages. The characters q, w and x appear only in foreign words. The háček (ˇ) is used with certain letters to form new characters: š, ž, and č, as well as ň, ě, ř, ť, and ď (the latter five uncommon outside Czech). The last two letters are sometimes written with a comma above (ʼ, an abbreviated háček) because of their height. The character ó exists only in loanwords and onomatopoeia.

Question:
What have some of Czech's characters been used for by phonologists to denote?

corresponding sounds in other languages