diff --git a/kfet/static/kfet/js/kfet.api.js b/kfet/static/kfet/js/kfet.api.js
index f40ad20f..1d99aaae 100644
--- a/kfet/static/kfet/js/kfet.api.js
+++ b/kfet/static/kfet/js/kfet.api.js
@@ -171,8 +171,8 @@ class ModelObject {
      * Returns a string value for the model, to use in comparisons
      * @see {@link Models.TreeNode.compare|TreeNode.compare}
      */
-    comparevalue() {
-        return this.id.toString();
+    static compare(a, b) {
+        return a.id - b.id;
     }
 }
 
@@ -520,15 +520,11 @@ class Article extends ModelObject {
 
     /**
      * Default values for Article model instances.
-     * @default <tt>{ 'id': 0, 'name': '', 'price': 0, 'stock': 0,
-     *          'category': new ArticleCategory() }</tt>
+     * @default <tt>{ 'id': 0, 'name': '', 'price': 0, 'stock': 0 }</tt>
      * @see {@link Models.ModelObject.default_data|ModelObject.default_data}
      */
     static get default_data() {
-        return {
-            'id': 0, 'name': '', 'price': 0, 'stock': 0,
-            'category': new ArticleCategory(),
-        };
+        return { 'id': 0, 'name': '', 'price': 0, 'stock': 0 };
     }
 
     /**
@@ -603,13 +599,43 @@ class Day extends ModelObject {
     set date(v) { this._date = dateUTCToParis(v).startOf('date'); }
 }
 
-
 /**
- * OperationGroup model. Cannot be accessed through API.
+ * HistoryGroup model. Should not be used without extending.
  * @extends Models.ModelObject
  * @memberof Models
  */
-class OperationGroup extends ModelObject {
+class HistoryGroup extends ModelObject {
+    static get props() {
+        return ['id', 'at', 'comment', 'valid_by'];
+    }
+
+    static get default_data() {
+        return {'id': 0, 'at': moment(), 'comment': '', 
+            'valid_by': '',};
+    }
+
+    /**
+     * Comparison function between OperationGroup model instances.
+     * @see {@link Models.ModelObject.compare|ModelObject.compare}
+     */
+    static compare(a, b) {
+        //Groups are sorted by most recent first
+        if (a.at < b.at) return 1;
+        else if (a.at > b.at) return -1;
+        else return 0;
+    }
+
+    // Parse the date to a moment() object
+    get at()  { return this._at; }
+    set at(v) { this._at = dateUTCToParis(v); }
+}
+
+/**
+ * OperationGroup model. Cannot be accessed through API.
+ * @extends Models.HistoryGroup
+ * @memberof Models
+ */
+class OperationGroup extends HistoryGroup {
 
     /**
      * Properties associated with an opegroup.
@@ -618,8 +644,7 @@ class OperationGroup extends ModelObject {
      * @see {@link Models.ModelObject.props|ModelObject.props}
      */
     static get props() {
-        return ['id', 'amount', 'at', 'is_cof', 'comment', 
-        'trigramme', 'valid_by', 'day', 'type'];
+        return HistoryGroup.props.concat(['is_cof', 'trigramme']);
     }
 
     /**
@@ -629,18 +654,10 @@ class OperationGroup extends ModelObject {
      * @see {@link Models.ModelObject.default_data|ModelObject.default_data}
      */
     static get default_data() {
-        return {'id': '', 'amount': 0, 'at': moment(), 'is_cof': false, 
-            'comment': '', 'trigramme': '', 'valid_by': '', 'day': new Day(),
-            'type': ''};
+        return $.extend({}, HistoryGroup.default_data, 
+                            {'amount': 0, 'is_cof': false, 'trigramme': ''});
     }
 
-    /**
-     * Verbose name for OperationGroup model.
-     * @default <tt>'opegroup'</tt>
-     * @see {@link Models.ModelObject.verbose_name|ModelObject.verbose_name}
-     */
-    static get verbose_name() { return 'opegroup'; }
-
     /**
      * @default {@link Formatters.OpegroupFormatter}
      */
@@ -648,27 +665,27 @@ class OperationGroup extends ModelObject {
         return OpegroupFormatter;
     }
 
-    /**
-     * Comparison function between OperationGroup model instances.
-     * @see {@link Models.ModelObject.compare|ModelObject.compare}
-     */
-    static compare(a, b) {
-        //Opegroups are sorted by most recent first
-        if (a.at < b.at) return 1;
-        else if (a.at > b.at) return -1;
-        else return 0;
-    }
-
     get amount()  { return this._amount; }
     set amount(v) { this._amount = floatCheck(v); }
-
-    // Parse the date to a moment() object
-    get at()  { return this._at; }
-    set at(v) { this._at = dateUTCToParis(v); }
 }
 
 /**
- * Operation model. Cannot be accessed through API.
+ * TransferGroup model. Cannot be accessed through API.
+ * @extends Models.HistoryGroup
+ * @memberof Models
+ */
+class TransferGroup extends HistoryGroup {
+    
+    /**
+     * @default {@link Formatters.TransferGroupFormatter}
+     */
+    formatter() {
+        return TransferGroupFormatter;
+    }
+}
+
+/**
+ * Operation model. Should not be used directly.
  * @extends Models.ModelObject
  * @memberof Models
  */
@@ -682,13 +699,7 @@ class Operation extends ModelObject {
      * @see {@link Models.ModelObject.props|ModelObject.props}
      */
     static get props() {
-        var common = ['id', 'type', 'amount', 'canceled_at', 'canceled_by',
-                      'is_checkout', 'opegroup'];
-        var transfer_only = ['from_acc', 'to_acc'];
-        var purchase_only = ['article_name', 'article_nb', 'addcost_for', 
-                             'addcost_amount'];
-
-        return common.concat(transfer_only, purchase_only);
+        return ['id', 'amount', 'canceled_at', 'canceled_by'];
     }
 
     /**
@@ -699,33 +710,12 @@ class Operation extends ModelObject {
      * @see {@link Models.ModelObject.default_data|ModelObject.default_data}
      */
     static get default_data() {
-        var common = {'id': '', 'type': '', 'amount': 0, 'is_checkout': false,
-            'canceled_at': undefined, 'canceled_by': '', 
-            'opegroup': new OperationGroup()}; 
-        var transfer_only = {'from_acc': '', 'to_acc': ''};
-        var purchase_only = {'article_name': '', 'article_nb': 0,
-            'addcost_amount': 0, 'addcost_for': 0};
-
-        return $.extend({}, common, transfer_only, purchase_only);
-    }
-
-    static get verbose_name() { return 'operation'; }
-
-    formatter() {
-        if (this.type === 'purchase')
-            return PurchaseFormatter;
-        else if (this.type == 'transfer')
-            return TransferFormatter;
-        else
-            return SpecialOpeFormatter;
+        return {'id': '', 'amount': 0, 'canceled_at': undefined, 'canceled_by': '' };
     }
 
     get amount()  { return this._amount; }
     set amount(v) { this._amount = floatCheck(v); }
 
-    get addcost_amount()  { return this._addcost_amount; }
-    set addcost_amount(v) { this._addcost_amount = floatCheck(v); }
-
     get canceled_at()  { return this._canceled_at; }
     set canceled_at(v) {
         if (v) 
@@ -735,6 +725,53 @@ class Operation extends ModelObject {
     }
 }
 
+class Purchase extends Operation {
+    static get props() {
+        return Operation.props.concat(
+                ['article_name', 'article_nb', 'addcost_amount', 'addcost_for']
+                );
+    }
+
+    static get default_data() {
+        return $.extend({}, Operation.default_data, {
+            'article_name': '', 'article_nb': 0,
+            'addcost_amount': 0, 'addcost_for': ''
+        });
+    }
+
+    formatter() {
+        return PurchaseFormatter;
+    }
+}
+
+class SpecialOperation extends Operation {
+    static get props() {
+        return Operation.props.concat(['type', 'is_checkout']);
+    }
+
+    static get default_data() {
+        return $.extend({}, Operation.default_data, {'type': '', 'is_checkout': false});
+    }
+
+    formatter() {
+        return SpecialOpeFormatter;
+    }
+}
+
+class Transfer extends Operation {
+    static get props() {
+        return Operation.props.concat(['from_acc', 'to_acc']);
+    }
+
+    static get default_data() {
+        return $.extend({}, Operation.default_data, {'from_acc': '', 'to_acc': ''});
+    }
+
+    formatter() {
+        return TransferFormatter;
+    }
+}
+
 
 /**
  * Node for ModelForest object
@@ -805,7 +842,9 @@ class ModelForest {
         var node = new TreeNode(data.type, content);
 
         if (data.child_sort)
-            node.child_sort = data.child_sort
+            node.child_sort = this.constructor.models[data.child_sort];
+        else
+            node.child_sort = ModelObject;
 
         if (direction <= 0) {
             if (data.parent) {
@@ -864,7 +903,7 @@ class ModelForest {
         $container.append($rendered);
 
         //dirty
-        node.children.sort(this.constructor.compare.bind(null, this.constructor.models[node.child_sort]));
+        node.children.sort(this.constructor.compare.bind(null, node.child_sort));
 
         for (let child of node.children) {
             var $child = this.render_element(child, templates, options);
@@ -1018,14 +1057,21 @@ class ArticleList extends APIModelForest {
  * @extends Models.APIModelList
  * @memberof Models
  */
-class OperationList extends APIModelList {
+class OperationList extends APIModelForest {
     /**
      * Default structure for OperationList instances.
      * @default <tt>[Operation, OperationGroup, Day]</tt>
      * @see {@link Models.ModelList.models|ModelList.models}
      */
     static get models() {
-        return [Operation, OperationGroup, Day];
+        return {
+            'day': Day,
+            'opegroup': OperationGroup,
+            'transfergroup': TransferGroup,
+            'purchase': Purchase,
+            'specialope': SpecialOperation,
+            'transfer': Transfer,
+        };
     }
 
     /**
@@ -1036,6 +1082,11 @@ class OperationList extends APIModelList {
     static get url_model() {
         return Urls['kfet.history.json']();
     }
+
+    constructor() {
+        super();
+        this.root_sort = Day;
+    }
 }
 
 
@@ -1331,20 +1382,7 @@ class ArticleFormatter extends Formatter {
  * @todo don't display trigramme in account_read
  */
 
-//TODO display_trigramme option
-class OpegroupFormatter extends Formatter {
-
-    /**
-     * Properties renderable to html.
-     * @default {@link Models.Opegroup.props}
-     */
-    static get props() { 
-        return OperationGroup.props.concat(['time']); 
-    }
-
-    static prop_amount(a) {
-        return amountDisplay(a.amount, a.is_cof, a.trigramme);
-    }
+class HistoryGroupFormatter extends Formatter {
 
     static prop_time(a) {
         return a.at.format('HH:mm:ss');
@@ -1358,6 +1396,29 @@ class OpegroupFormatter extends Formatter {
     }
 }
 
+class TransferGroupFormatter extends HistoryGroupFormatter {
+    
+    static get props() {
+        return TransferGroup.props.concat(['infos', 'time']);
+    }
+
+    static prop_infos(a) {
+        //TODO find better thing to put here
+        return 'Transferts';
+    }
+}
+
+class OpegroupFormatter extends HistoryGroupFormatter {
+
+    static get props() {
+        return OperationGroup.props.concat(['time']);
+    }
+
+    static prop_amount(a) {
+        return amountDisplay(a.amount, a.is_cof, a.trigramme);
+    }
+}
+
 /**
  * @extends Formatters.Formatter
  * @memberof Formatters
@@ -1393,12 +1454,12 @@ class OperationFormatter extends Formatter {
     }
 
     static prop_amount(a) {
-        return amountDisplay(a.amount, a.opegroup.is_cof, a.opegroup.trigramme);
+        return amountDisplay(a.amount, a.is_cof, a.trigramme);
     }
 
     static prop_addcost(a) {
         if (a.addcost_for) {
-            return '('+amountDisplay(a.addcost_amount, a.opegroup.is_cof)
+            return '('+amountDisplay(a.addcost_amount, a.is_cof)
                     +'UKF pour '+a.addcost_for+')';
         } else {
             return '';