diff --git a/src/engine/Period.h b/src/engine/Period.h
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+/*
+ * FILE:
+ * Period.h
+ *
+ * FUNCTION:
+ * Implement accounting periods.
+ *
+ * CAUTION: this is currently a non-functioning, experimental implementation
+ * of the design described in src/doc/book.txt
+ *
+ * HISTORY:
+ * created by Linas Vepstas November 2001
+ * Copyright (c) 2001 Linas Vepstas <linas@linas.org>
+ */
+
+
+#ifndef XACC_PERIOD_H
+#define XACC_PERIOD_H
+
+#include "gnc-book.h"
+#include "gnc-engine.h"
+#include "Query.h"
+
+
+/* The gnc_book_calve_period() routine will split the indicated
+ *    book into two books, returning a newly created book with 
+ *    the older transactions placed in it. 
+ *
+-- It will use the /book/blah-blah kvp value to denote xxx.
+-- Make an equity transfer so that we can carry forward the balances.
+/book/close-date
+/book/closing-balance-of-account-guid
+/book/previous-guid
+/book/name=some-user-supplied-name
+/book/notes=user-supplied-descriptive-comments
+/book/start-date=xxx
+/book/end-date=xxx
+/book/previous-book-guids=(list 0xa 0xb 0xc)
+/book/accounting-period=enum {none, week, month, quarter, trimester, year}
+
+
+ */
+GNCBook * gnc_book_calve_period (GNCBook *, Timespec);
+
+/* The gnc_book_partition() uses the result of the indicated query
+ *    to partition an existing book into two parts.  It returns 
+ *    a newly created book, containing a copy of all of the accounts,
+ *    and it moves all of the transactions returned by the query to 
+ *    the copied accounts in the copied book.   Any query will work
+ *    to partition a book; however, its expected that this routine 
+ *    will mostly serve as a utility to break up a book into 
+ *    accounting periods. 
+ *
+ *    This routine intentionally does not copy scheduled/recurring 
+ *    transactions.
+ *
+ *    When an account is copied, the copy is issued a new GUID.
+ *    The GUID of its sibling is placed in the 'gemini' KVP value
+ *    (See kvp_doc.txt for more detail).   Transactions and splits
+ *    are moved without reassigning them a new GUID.  Note they
+ *    are removed from one book's entity table and placed into the 
+ *    other book:  Once moved, they won't be findable in the entity
+ *    table of the old book.
+ */
+GNCBook * gnc_book_partition (GNCBook *, Query *);
+
+/* The gnc_book_insert_trans() routine takes an existing transaction
+ *    that is located in one book, and moves it to another book.
+ *    It moves all of the splits as well.  In the course of the 
+ *    move, the transaction is literally deleted from the first 
+ *    book as its placed into the second.  The transaction and
+ *    split GUID's are not changed in the move.  This routine 
+ *    assumes that twin accounts already exist in both books 
+ *    (and can be located with the standard twining proceedure).
+ */
+
+void gnc_book_insert_trans (GNCBook *book, Transaction *trans);
+
+#endif /* XACC_PERIOD_H */
+