The correct spelling of the phrase "art source of" can be explained using IPA phonetic transcription. The first word, "art," is spelled with the /ɑː/ vowel sound, as in "car" or "bar." The word "source" is pronounced with a long /ɔː/ sound, as in "horse" or "law." Lastly, "of" is spelled with a short /ɒ/ sound, like the "o" in "hot" or "not." So when written out phonetically, "art source of" is spelled as /ɑːt sɔːs ɒv/.