Question:
Who was the chair of Economic Community of West African States in Aug, 1981?

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

Answer:
Siaka Probyn Stevens