-melm 604 Subject,Subject:p
-melm 605 Subject,Subject:p
-melm 606 Subject,Subject:p
-melm 607 Subject,Subject:p
-melm 630 Subject,Subject:p
-melm 631 Subject,Subject:p
-melm 632 Subject,Subject:p
-melm 633 Subject,Subject:p
-melm 634 Subject,Subject:p
-melm 635 Subject,Subject:p
-melm 636 Subject,Subject:p
-melm 610 Subject,Subject:p
-melm 640 Subject,Subject:p
-melm 641 Subject,Subject:p
-melm 642 Subject,Subject:p
-melm 643 Subject,Subject:p
-melm 644 Subject,Subject:p
-melm 645 Subject,Subject:p
-melm 646 Subject,Subject:p
-
-######################
-
-melm 676$a Dewey-classification:w,Dewey-classification:s
+melm 604 Subject,Subject:p
+melm 605 Subject,Subject:p
+melm 606 Subject,Subject:p
+melm 607 Subject,Subject:p
+melm 608 Subject,Subject:p
+melm 610 Subject,Subject:p
+melm 615 Subject,Subject:p
+melm 616 Subject,Subject:p
+melm 617 Subject,Subject:p
+melm 620 Subject,Subject:p
+melm 621 Subject,Subject:p
+# Technical details access // see Marc21 753. Seems deprecated.
+# melm 626 Subject,Subject:p
+# Geographic area code // see Marc21 043. Probably not useful
+# melm 660 Subject,Subject:p
+# Chronological coverage code. Probably not useful
+# melm 661 Subject,Subject:p
+
+#FIXME Fields 603, 630, 631, 632, 633, 634, 635, 636, 646 are not defined in Unimarc, but may be used by some libraries.
+melm 603 Subject,Subject:p
+melm 630 Subject,Subject:p
+melm 631 Subject,Subject:p
+melm 632 Subject,Subject:p
+melm 633 Subject,Subject:p
+melm 634 Subject,Subject:p
+melm 635 Subject,Subject:p
+melm 636 Subject,Subject:p
+melm 646 Subject,Subject:p
+
+########### CLASSIFICATIONS (67x/68x) ##################
+# PRECIS
+melm 670 Subject-precis:w,Subject-precis:p
+# Universal Decimal Classification // see Marc21 080
+melm 675$a UDC-classification:w,UDC-classification:p,UDC-classification:s
+# Dewey // see Marc21 082
+melm 676$a Dewey-classification:w,Dewey-classification:p,Dewey-classification:s
+# LC // see Marc21 050
+melm 680$b LC-call-number:s
+melm 680 LC-call-number:w,LC-call-number:p
+# Other class numbers // see Marc21 084
+melm 686 Local-classification:w,Local-classification:p