Question:
Who was the chair of Economic Community of West African States in Apr, 1984?

Context:
 Nicéphore Soglo is the chair of Economic Community of West African States from Jan, 1993 to Jan, 1994. 
 Alassane Dramane Ouattara is the chair of Economic Community of West African States from Feb, 2012 to Feb, 2013. 
 Mamadou Tandja is the chair of Economic Community of West African States from Jan, 2005 to Jan, 2007. 
 Olusegun Obasanjo is the chair of Economic Community of West African States from Sep, 1977 to Sep, 1979. 
 Mathieu Kérékou is the chair of Economic Community of West African States from Jan, 1982 to Jan, 1983. 
 Mahamadou Issoufou is the chair of Economic Community of West African States from Jun, 2019 to Jun, 2020. 
 Umaru Musa Yar'Adua is the chair of Economic Community of West African States from Dec, 2008 to Feb, 2010. 
 Lansana Conté is the chair of Economic Community of West African States from Jan, 1984 to Jan, 1985. 
 Ellen Johnson Sirleaf is the chair of Economic Community of West African States from Jun, 2016 to Jun, 2017. 
 Siaka Probyn Stevens is the chair of Economic Community of West African States from Jan, 1981 to Jan, 1982. 
 Faure Essozimna Gnassingbé Eyadéma is the chair of Economic Community of West African States from Jun, 2017 to Jul, 2018. 
 Alpha Oumar Konaré is the chair of Economic Community of West African States from Jan, 1999 to Dec, 2001. 
 Ahmed Sékou Touré is the chair of Economic Community of West African States from Jan, 1983 to Jan, 1984. 
 Abdou Diouf is the chair of Economic Community of West African States from Jan, 1992 to Jan, 1993. 
 Léopold Sédar Senghor is the chair of Economic Community of West African States from Sep, 1979 to Dec, 1980. 
 Macky Sall is the chair of Economic Community of West African States from May, 2015 to Jun, 2016. 
 Goodluck Jonathan is the chair of Economic Community of West African States from Feb, 2010 to Feb, 2012. 
 Yakubu Gowon is the chair of Economic Community of West African States from May, 1975 to Jul, 1975. 
 John Mahama is the chair of Economic Community of West African States from Feb, 2013 to May, 2015. 
 Jerry Rawlings is the chair of Economic Community of West African States from Jan, 1994 to Jul, 1996. 
 Nana Akufo-Addo is the chair of Economic Community of West African States from Jun, 2020 to Dec, 2022. 
 Abdoulaye Wade is the chair of Economic Community of West African States from Dec, 2001 to Jan, 2003. 
 Étienne Gnassingbé Eyadéma is the chair of Economic Community of West African States from Jan, 1999 to Jan, 1999. 
 Abdulsalami Abubakar is the chair of Economic Community of West African States from Jun, 1998 to Jan, 1999. 
 Muhammadu Buhari is the chair of Economic Community of West African States from Jul, 2018 to Jun, 2019. 
 Blaise Compaoré is the chair of Economic Community of West African States from Jan, 2007 to Dec, 2008. 
 John Kufuor is the chair of Economic Community of West African States from Jan, 2003 to Jan, 2005. 
 Sani Abacha is the chair of Economic Community of West African States from Jul, 1996 to Jun, 1998.

Answer:
Lansana Conté