} else if( x instanceof Variable ){
Product p = new Product( (Variable)x, true );
return p.multiply( (Complex)this );
} else if( x instanceof Sum ){
Product p = new Product( (Expression)x, true );
return p.multiply( this );
} else if( x instanceof Product ){
Product p = new Product( (Expression)x, true );
return p.multiply( (Complex)this );
} else if( x instanceof Expression ){
Product p = new Product( (Expression)x, true );