Does anybody can help me for my below errors:

Notice: Only variables should be assigned by reference in file /modules/system/admin/preferences/main.php line 78

Notice: Only variables should be assigned by reference in file /class/xoopslists.php line 200

Notice: Only variables should be assigned by reference in file /kernel/module.php line 542

Notice: Only variables should be assigned by reference in file /modules/system/admin/preferences/main.php line 161

Notice: Only variables should be assigned by reference in file /kernel/tplset.php line 193

Notice: Only variables should be assigned by reference in file /modules/system/admin/preferences/main.php line 142

Notice: Only variables should be assigned by reference in file /modules/system/admin/preferences/main.php line 94

Notice: Only variables should be assigned by reference in file /modules/system/admin/preferences/main.php line 94

Notice: Only variables should be assigned by reference in file /modules/system/admin/preferences/main.php line 94

Notice: Only variables should be assigned by reference in file /modules/system/admin/preferences/main.php line 180