Alexander Grothendieck , author of the theories upon which some of the above works are based , became a recluse in 1991 .
Alexander Grothendieck , author of the theories upon which some of the above works are based , removed his published works from circulation .
Alexander Grothendieck , author of the theories upon which some of the above works are based , became a recluse in 1991 and removed his published works from circulation .