ɐ nˈaɪntiːnhˈʌndɹɪd nˈaɪnti ˈeɪt stˈʌdi baɪ stˈiːvɛnsən ˈɛt ˈæl. vˈɛɹᵻfˌaɪd ðə pɹˈɛzəns ʌv lˌæ æt sˈiː sˈɛvənti tˈuː æz wˈɛl æz lˌæ tˈuː æt sˈiː sˈɛvənti tˈuː, bˌʌt ˈɛmptikˈeɪdʒ sˈiː sˈɛvənti tˈuː wʌz ˈæbsənt, bˈeɪst ˌɔn lˈeɪzɚ dᵻsˈoːɹpʃən mˈæs spɛktɹˈɑːmətɹi ænd jˌuːvˈiː mˈaɪnəs vˈɪs spɛktɹˈɑːskəpi.
A 1998 study by Stevenson et al. verified the presence of La@C72 as well as La2@C72, but empty-cage C72 was absent, based on laser desorption mass spectrometry and UV−vis spectroscopy.