private function totalIndisWithSourcesQuery(): int
    {
        return DB::table('individuals')
            ->select(['i_id'])
            ->distinct()
            ->join('link', static function (JoinClause $join): void {
                $join->on('i_id', '=', 'l_from')
                    ->on('i_file', '=', 'l_file');
            })
            ->where('l_file', '=', $this->tree->id())
            ->where('l_type', '=', 'SOUR')
            ->count('i_id');
    }