On the Borel class of the derived set operator
1982 ◽
Vol 79
◽
pp. 357-380
◽
1983 ◽
Vol 79
◽
pp. 367-372
◽
1989 ◽
Vol 199
◽
pp. 495-518
◽
2002 ◽
Vol 30
(2)
◽
pp. 120-130
◽
Keyword(s):
1975 ◽
Vol 97
(3)
◽
pp. 873-880
◽
Keyword(s):
1970 ◽
Vol 35
(3)
◽
pp. 571-574
◽