CREATE TABLE keyword (keyword VARCHAR, kid INT)
CREATE TABLE domain (did INT, name VARCHAR)
CREATE TABLE domain_keyword (did INT, kid INT)
CREATE TABLE journal (homepage VARCHAR, jid INT, name VARCHAR)
CREATE TABLE cite (cited INT, citing INT)
CREATE TABLE domain_conference (cid INT, did INT)
CREATE TABLE author (aid INT, homepage VARCHAR, name VARCHAR, oid INT)
CREATE TABLE domain_journal (did INT, jid INT)
CREATE TABLE conference (cid INT, homepage VARCHAR, name VARCHAR)
CREATE TABLE publication (abstract VARCHAR, cid INT, citation_num INT, jid INT, pid INT, reference_num INT, title VARCHAR, year INT)
CREATE TABLE domain_author (aid INT, did INT)
CREATE TABLE organization (continent VARCHAR, homepage VARCHAR, name VARCHAR, oid INT)
CREATE TABLE publication_keyword (kid INT, pid INT)
CREATE TABLE writes (aid INT, pid INT)
CREATE TABLE domain_publication (did INT, pid INT)

return me the author in the ' University of Michigan ' whose papers have the most total citations .
SELECT author.name FROM author, organization, publication, writes WHERE organization.name = 'University of Michigan' AND organization.oid = author.oid AND writes.aid = author.aid AND writes.pid = publication.pid GROUP BY author.name ORDER BY SUM(publication.citation_num) DESC LIMIT 1
SELECT "author"."name" FROM "author" JOIN "organization" ON "author"."oid" = "organization"."oid" AND "organization"."name" = 'University of Michigan' JOIN "writes" ON "author"."aid" = "writes"."aid" JOIN "publication" ON "publication"."pid" = "writes"."pid" GROUP BY "author"."name" ORDER BY SUM("publication"."citation_num") DESC NULLS LAST LIMIT 1