--- trunk/doc/formating_xml.txt	2003/02/23 06:50:55	23
+++ trunk/doc/formating_xml.txt	2003/02/23 06:55:00	24
@@ -24,7 +24,7 @@
 		default: len - rest of the string
 	
 	skip2nr
-		skip all aphanumeric caracters and return just
+		skip all alphanumeric characters and return just
 		numbers after it. To output "1992." from "cop. 1992."
 
 	initial	[word_nr[,...]]
@@ -36,3 +36,19 @@
 
 filter:
 	name of filter which is stored in filters/[name].pm
+
+
+Fields
+
+Fields which are read from isis are in format 999x where 999 is three
+digit ISIS field and x is isis subfield. There are three special ISIS
+fields supported: 10 and 11 (used for ISBN and ISSN, those are only
+fields which have just two digits) and MFN which returns ISIS MFN.
+
+
+Formatting fields
+
+It's done using simple algorithm: it first selects prefix and then
+inserts fields (and their separators) or just skips them (so it groups
+fields and separator right from it). At end it just appends suffix.
+