var authorLitWorks = from litwork in _context.LitWorks.Include(la => la.LitWorkAuthors).ThenInclude(a => a.Author)
join authorLitwork in _context.LitWorkAuthors on litwork.LitWorkId equals authorLitwork.LitWorkId
join theAuthor in _context.Authors on authorLitwork.AuthorId equals theAuthor.AuthorId
//where authorLitwork.AuthorId == id
group theAuthor by new { litwork.LitWorkId, litwork.Title, } into lw
select new LitWorkWithAuthors { LitWorkId = lw.Key.LitWorkId, Title = lw.Key.Title, Authors = string.Join(",", _context.Authors.Select(s => s.FullName)) };