I am trying to search case,solution and KnowledgeArticles with following SOSL
FIND 'lithium' RETURNING Dissusion__kav (Title, Summary, LastPublishedDate, KnowledgeArticleId, UrlName WHERE PublishStatus = 'Online'), questionAndAnswer__kav (Title, Summary, LastPublishedDate, KnowledgeArticleId, UrlName WHERE PublishStatus = 'Online'), Case__kav (Title, Summary, LastPublishedDate, KnowledgeArticleId, UrlName WHERE PublishStatus = 'Online')
but on executing I am getting this Exception
You must specify a language WHERE clause for knowledge articles in this API version
But WHERE clause is already included .