"The puzzle of Ngäbére auxiliaries: Grammatical reconstruction in Chibchan and Misumalpan", in William Croft, Suzanne Kemmer and Keith Denning, eds., "Studies in Typology and Diachrony: Papers presented to Joseph H. Greenberg on his 75th birthday", "Typological Studies in Language" 20, John Benjamins 1990.
«The puzzle of Ngäbére auxiliaries: Grammatical reconstruction in Chibchan and Misumalpan», in William Croft, Suzanne Kemmer and Keith Denning, eds., "Studies in Typology and Diachrony: Papers presented to Joseph H. Greenberg on his 75th birthday", Typological Studies in Language 20, John Benjamins 1990.