↑ 4.04.1Byrd, Andrew Miles (2015) The Indo-European Syllable (Brill's Studies in Indo-European Languages & Linguistics; 15), Leiden: Brill, page 276: “*terh₂-”
^ Mallory, J. P. with Adams, D. Q. (2006) “*terh₂-”, in The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World (Oxford Linguistics), New York: Oxford University Press, →ISBN, page 289
↑ 7.07.17.27.3Guus Kroonen (2013) “*þerhwe ~ *þurhwe”, in Alexander Lubotsky, editor, Etymological Dictionary of Proto-Germanic (Leiden Indo-European Etymological Dictionary Series; 11)[2], Leiden, Boston: Brill, →ISBN, pages 538-539
^ Elbourne, Paul (2000) “Plain Voiceless Stop plus Laryngeal in Indo-European”, in Historische Sprachforschung / Historical Linguistics, volume 113, Vandenhoeck & Ruprecht, →JSTOR, page 13: “*térH₂-e-ti”
↑ 9.09.1Malzahn, Melanie (2016) “Tudáti-presents and the tēzzi Principle”, in Sahasram Ati Srajas. Indo-Iranian and Indo-European Studies in Honor of Stephanie W. Jamison[3], Ann Arbor, New York: Beech Stave Press, page 227: “*tērh₂-/*trēh₂-; *térh₂-ti/*tr̥h₂-énti”
↑ 10.010.110.2Kulikov, Leonid (2017) “Part 4 Chapter 2: Indo-Aryan”, in Kapović, Mate, editor, The Indo-European Languages (Routledge Language Family Series), 2nd edition, London, New York: Routledge, →ISBN, page 224: “*-tr̥h₂-e-; *e-tērh₂-s-; *-tr̥h₂-no-”
↑ 11.011.1Schumacher, Stefan, Schulze-Thulin, Britta (2004) Die keltischen Primärverben: ein vergleichendes, etymologisches und morphologisches Lexikon [The Celtic Primary Verbs: A comparative, etymological and morphological lexicon] (Innsbrucker Beiträge zur Sprachwissenschaft; 110) (in German), Innsbruck: Institut für Sprachen und Literaturen der Universität Innsbruck, →ISBN, page 620: “*tar-i̯e/o-”
^ Sihler, Andrew L. (1995) New Comparative Grammar of Greek and Latin, Oxford, New York: Oxford University Press, →ISBN, page 95: “'tr̥H₂-yᵉ/ₒ-”
^ Lubotsky, Alexander (2011) “tar¹ (tur) {1”, in The Indo-Aryan Inherited Lexicon (in progress) (Indo-European Etymological Dictionary Project), Leiden University}
^ Beekes, Robert S. P. (2010) “νέκταρ, -αρος”, in Etymological Dictionary of Greek (Leiden Indo-European Etymological Dictionary Series; 10), with the assistance of Lucien van Beek, Leiden, Boston: Brill, →ISBN, pages 1004-1005: “*neḱ-trh₂-os”
^ Orel, Vladimir E. (2000) A concise historical grammar of the Albanian language: reconstruction of Proto-Albanian[4], Leiden, Boston, Köln: Brill, →ISBN, page 192: “*t(e)ratja”