diff --git a/source/app/controllers/helper.py b/source/app/controllers/helper.py
index 122828a..6ba1863 100644
--- a/source/app/controllers/helper.py
+++ b/source/app/controllers/helper.py
@@ -313,7 +313,10 @@ class SendMail(object):
             message.attach(MIMEText(options['mensaje'], 'html'))
             for f in options['files']:
                 part = MIMEBase('application', 'octet-stream')
-                part.set_payload(f[0])
+                if isinstance(f[0], str):
+                    part.set_payload(f[0].encode('utf-8'))
+                else:
+                    part.set_payload(f[0])
                 encoders.encode_base64(part)
                 part.add_header(
                     'Content-Disposition',
diff --git a/source/app/controllers/util.py b/source/app/controllers/util.py
index f2ebcf9..29fd528 100644
--- a/source/app/controllers/util.py
+++ b/source/app/controllers/util.py
@@ -1061,24 +1061,23 @@ class LIBO(object):
         self._template.setPrinter(self._set_properties({'PaperFormat': LETTER}))
         self._render(data)
 
-        # ~ path = '{}.ods'.format(tempfile.mkstemp()[1])
-        path = get_path_temp('.ods')
-        self._template.storeToURL(self._path_url(path), ())
+        path_ods = get_path_temp('.ods')
+        self._template.storeToURL(self._path_url(path_ods), ())
         if ods:
-            data = self._read(path)
-            _kill(path)
+            data = self._read(path_ods)
+            _kill(path_ods)
             return data
 
-        doc = self._doc_open(path, {'Hidden': True})
+        doc = self._doc_open(path_ods, {'Hidden': True})
         options = {'FilterName': 'calc_pdf_Export'}
-        # ~ path = tempfile.mkstemp()[1]
-        path = get_path_temp('.pdf')
-        doc.storeToURL(self._path_url(path), self._set_properties(options))
+        path_pdf = get_path_temp('.pdf')
+        doc.storeToURL(self._path_url(path_pdf), self._set_properties(options))
         doc.close(True)
         self._template.close(True)
 
-        data = self._read(path)
-        _kill(path)
+        data = self._read(path_pdf)
+        _kill(path_ods)
+        _kill(path_pdf)
         return data
 
     def _get_data(self, doc, name=0):
@@ -1674,7 +1673,8 @@ def _nomina(doc, data, values, version_cfdi):
     info = CaseInsensitiveDict(node_nomina.attrib.copy())
 
     node = node_nomina.find('{}Emisor'.format(PRE['NOMINA'][version]))
-    data['emisor'].update(CaseInsensitiveDict(node.attrib.copy()))
+    if not node is None:
+        data['emisor'].update(CaseInsensitiveDict(node.attrib.copy()))
 
     node = node_nomina.find('{}Receptor'.format(PRE['NOMINA'][version]))
     data['receptor'].update(CaseInsensitiveDict(node.attrib.copy()))
diff --git a/source/app/models/main.py b/source/app/models/main.py
index 8df1219..a1b5c72 100644
--- a/source/app/models/main.py
+++ b/source/app/models/main.py
@@ -136,44 +136,31 @@ def import_invoice():
     if not rows:
         return {'ok': False, 'msg': msg}
 
-    # ~ clave, descripcion, precio, cantidad
-    products = {}
+    products = []
     for row in rows:
         try:
             obj = Productos.get(Productos.clave==row[0])
-            if obj.id in products:
-                vu = round(row[2], 2)
-                descuento = round(row[3], 2)
-                cant = round(row[4], 2)
-                pf =  products[obj.id]['valor_unitario'] - descuento
-                products[obj.id]['cantidad'] += cant
-                products[obj.id]['importe'] = round(
-                    pf * products[obj.id]['cantidad'], DECIMALES)
-                if vu != products[obj.id]['valor_unitario']:
-                    msg = 'Precio diferente en producto: {}'.format(row[0])
-                    return {'ok': False, 'msg': msg}
-            else:
-                vu = round(row[2], 2)
-                descuento = round(row[3], 2)
-                cant = round(row[4], 2)
-                pf =  vu - descuento
-                p = {
-                    'id': obj.id,
-                    'delete': '-',
-                    'clave': obj.clave,
-                    'descripcion': obj.descripcion,
-                    'unidad': obj.unidad.name,
-                    'cantidad': cant,
-                    'valor_unitario': vu,
-                    'descuento': obj.descuento,
-                    'importe': round(pf * cant, DECIMALES),
-                    'taxes': _get_taxes_product(obj.id),
-                }
-                products[obj.id] = p
+            vu = round(row[2], 2)
+            descuento = round(row[3], 2)
+            cant = round(row[4], 2)
+            pf =  vu - descuento
+            p = {
+                'id_product': obj.id,
+                'delete': '-',
+                'clave': obj.clave,
+                'descripcion': obj.descripcion,
+                'unidad': obj.unidad.id,
+                'cantidad': cant,
+                'valor_unitario': vu,
+                'descuento': descuento,
+                'importe': round(pf * cant, DECIMALES),
+                'taxes': _get_taxes_product(obj.id),
+            }
+            products.append(p)
         except Productos.DoesNotExist:
             pass
     log.info('Factura importada...')
-    return {'ok': True, 'rows': tuple(products.values())}
+    return {'ok': True, 'rows': tuple(products)}
 
 
 def get_doc(type_doc, id, rfc):
@@ -246,6 +233,7 @@ def config_timbrar():
         'cfdi_tax_locales': Configuracion.get_bool('chk_config_tax_locales'),
         'cfdi_tax_decimals': Configuracion.get_bool('chk_config_tax_decimals'),
         'cfdi_with_taxes': Configuracion.get_bool('chk_config_price_with_taxes_in_invoice'),
+        'cfdi_add_same_product': Configuracion.get_bool('chk_config_add_same_product'),
     }
 
     return conf
@@ -333,6 +321,7 @@ class Configuracion(BaseModel):
                 'chk_config_tax_locales',
                 'chk_config_tax_decimals',
                 'chk_config_price_with_taxes_in_invoice',
+                'chk_config_add_same_product',
                 'chk_config_anticipo',
                 'chk_config_cuenta_predial',
                 'chk_config_codigo_barras',
@@ -2748,11 +2737,11 @@ class Productos(BaseModel):
         clave = values.get('key', '')
         row = (Productos
             .select(
-                Productos.id,
+                Productos.id.alias('id_product'),
                 Productos.clave,
                 Productos.clave_sat,
                 Productos.descripcion,
-                SATUnidades.name.alias('unidad'),
+                SATUnidades.id.alias('unidad'),
                 Productos.valor_unitario,
                 Productos.descuento)
             .join(SATUnidades).switch(Productos)
@@ -2761,7 +2750,7 @@ class Productos(BaseModel):
             .dicts()
         )
         if len(row):
-            id = row[0]['id']
+            id = row[0]['id_product']
             model_pt = Productos.impuestos.get_through_model()
             taxes = tuple(model_pt
                 .select(
@@ -3360,7 +3349,7 @@ class Facturas(BaseModel):
         }
         options = {
             'para': obj.cliente.correo_facturas,
-            'copia': values['correo_copia'],
+            'copia': values.get('correo_copia', ''),
             'confirmar': util.get_bool(values.get('correo_confirmacion', '0')),
             'asunto': util.make_info_mail(values['correo_asunto'], fields),
             'mensaje': util.make_info_mail(values['correo_mensaje'], fields),
@@ -3567,12 +3556,11 @@ class Facturas(BaseModel):
         locales_retenciones = 0
 
         for product in products:
-            # ~ print ('\n', product['descripcion'])
-            id_product = product.pop('id')
+            id_product = product.pop('id_product')
             id_student = product.pop('id_student', 0)
             p = Productos.get(Productos.id==id_product)
 
-            product['unidad'] = p.unidad.key
+            product['unidad'] = SATUnidades.get(SATUnidades.id==product['unidad']).key
             product['clave'] = p.clave
             product['clave_sat'] = p.clave_sat
             product['cuenta_predial'] = p.cuenta_predial
@@ -3793,8 +3781,8 @@ class Facturas(BaseModel):
                 'ClaveProdServ': row.producto.clave_sat,
                 'NoIdentificacion': row.producto.clave,
                 'Cantidad': FORMAT.format(row.cantidad),
-                'ClaveUnidad': row.producto.unidad.key,
-                'Unidad': row.producto.unidad.name[:20],
+                'ClaveUnidad': row.unidad,
+                'Unidad': SATUnidades.get(SATUnidades.key==row.unidad).name[:20],
                 'Descripcion': row.descripcion,
                 'ValorUnitario': FORMAT.format(row.valor_unitario),
                 'Importe': FORMAT.format(row.importe),
@@ -4467,10 +4455,10 @@ class PreFacturas(BaseModel):
         locales_retenciones = 0
 
         for product in products:
-            id_product = product.pop('id')
+            id_product = product.pop('id_product')
             p = Productos.get(Productos.id==id_product)
 
-            product['unidad'] = p.unidad.key
+            product['unidad'] = SATUnidades.get(SATUnidades.id==product['unidad']).key
             product['clave'] = p.clave
             product['clave_sat'] = p.clave_sat
             product['cuenta_predial'] = p.cuenta_predial
@@ -4717,16 +4705,16 @@ class PreFacturasDetalle(BaseModel):
             PreFacturasDetalle.factura==id)
 
         for p in reversed(productos):
-            row = {'id': p.producto.id}
+            row = {'id_product': p.producto.id}
             row['clave'] = p.producto.clave
             row['descripcion'] = p.descripcion
-            row['unidad'] = p.producto.unidad.name
+            row['unidad'] = p.producto.unidad.id
             row['cantidad'] = p.cantidad
             row['valor_unitario'] = p.valor_unitario
             row['descuento'] = p.descuento
             pf = p.valor_unitario - p.descuento
             row['importe'] = round(pf * p.cantidad, DECIMALES)
-            impuestos = cls._get_impuestos(cls, row['id'])
+            impuestos = cls._get_impuestos(cls, row['id_product'])
             data.append({'row': row, 'taxes': impuestos})
 
         return {'rows': data, 'receptor': receptor}
diff --git a/source/static/js/controller/admin.js b/source/static/js/controller/admin.js
index f1a8270..5e8786f 100644
--- a/source/static/js/controller/admin.js
+++ b/source/static/js/controller/admin.js
@@ -63,6 +63,7 @@ var controllers = {
         $$('chk_config_tax_locales').attachEvent('onItemClick', chk_config_item_click)
         $$('chk_config_tax_decimals').attachEvent('onItemClick', chk_config_item_click)
         $$('chk_config_price_with_taxes_in_invoice').attachEvent('onItemClick', chk_config_item_click)
+        $$('chk_config_add_same_product').attachEvent('onItemClick', chk_config_item_click)
         $$('chk_config_anticipo').attachEvent('onItemClick', chk_config_item_click)
         $$('chk_config_ine').attachEvent('onItemClick', chk_config_item_click)
         $$('chk_config_edu').attachEvent('onItemClick', chk_config_item_click)
diff --git a/source/static/js/controller/invoices.js b/source/static/js/controller/invoices.js
index 5b81709..df0e660 100644
--- a/source/static/js/controller/invoices.js
+++ b/source/static/js/controller/invoices.js
@@ -167,6 +167,7 @@ function default_config(){
         cfg_invoice['tax_locales'] = values.cfdi_tax_locales
         cfg_invoice['tax_decimals'] = values.cfdi_tax_decimals
         cfg_invoice['with_taxes'] = values.cfdi_with_taxes
+        cfg_invoice['add_same_product'] = values.cfdi_add_same_product
         if(values.cfdi_show_pedimento){
             $$('grid_details').showColumn('pedimento')
         }
@@ -558,10 +559,11 @@ function guardar_y_timbrar(values){
 
     var rows = grid.data.getRange()
     for (i = 0; i < rows.length; i++) {
+        delete rows[i]['id']
         delete rows[i]['delete']
         delete rows[i]['clave']
         delete rows[i]['clave_sat']
-        delete rows[i]['unidad']
+        //~ delete rows[i]['unidad']
         delete rows[i]['importe']
         delete rows[i]['student']
         rows[i]['valor_unitario'] = parseFloat(rows[i]['valor_unitario'])
@@ -808,7 +810,7 @@ function calcular_impuestos(){
         var import2 = (valor_unitario * cantidad).round(DECIMALES)
         var importe = parseFloat(product.importe)
         subtotal += importe
-        query = table_pt.chain().find({'product': product.id}).data()
+        query = table_pt.chain().find({'product': product.id_product}).data()
         for(var tax of query){
             impuesto = table_taxes.findOne({'id': tax.tax})
             if(impuesto.tipo == 'E'){
@@ -867,7 +869,16 @@ function set_product(values){
     var taxes = values.taxes
     var values = values.row
     var form = $$('form_invoice')
-    var row = grid.getItem(values.id)
+    var row = undefined
+
+    if(!cfg_invoice['add_same_product']){
+        for(var id in grid.data.pull){
+            if(grid.getItem(id).id_product == values.id_product){
+                row = grid.getItem(id)
+                break
+            }
+        }
+    }
 
     values['delete'] = '-'
     if (row == undefined){
@@ -946,7 +957,7 @@ function search_product_id_key_press(code, e){
 
 
 function grid_details_before_edit_start(id){
-    var columns = ['', 'descripcion', 'pedimento','cantidad', 'valor_unitario', 'descuento']
+    var columns = ['', 'unidad', 'descripcion', 'pedimento','cantidad', 'valor_unitario', 'descuento']
     if(!columns.indexOf(id.column)){
         return !this.getItem(id.row)[id.column]
     }
@@ -956,6 +967,10 @@ function grid_details_before_edit_start(id){
 function grid_details_before_edit_stop(state, editor){
     var row = grid.getItem(editor.row)
 
+    if(editor.column == 'unidad'){
+        return true
+    }
+
     if(editor.column == 'descripcion'){
         if(!state.value.trim()){
             msg = 'La descripción no puede estar vacía'
@@ -1358,9 +1373,9 @@ function cmd_prefactura_click(){
 
     var rows = grid.data.getRange()
     for (i = 0; i < rows.length; i++) {
+        delete rows[i]['id']
         delete rows[i]['delete']
         delete rows[i]['clave']
-        delete rows[i]['unidad']
         delete rows[i]['importe']
         rows[i]['valor_unitario'] = parseFloat(rows[i]['valor_unitario'])
         rows[i]['descuento'] = parseFloat(rows[i]['descuento'])
diff --git a/source/static/js/ui/admin.js b/source/static/js/ui/admin.js
index 3dbd7f9..e06351d 100644
--- a/source/static/js/ui/admin.js
+++ b/source/static/js/ui/admin.js
@@ -599,6 +599,8 @@ var options_admin_otros = [
             labelRight: 'Calcular impuestos con 4 decimales'},
         {view: 'checkbox', id: 'chk_config_price_with_taxes_in_invoice', labelWidth: 0,
             labelRight: 'Precio incluye impuestos'},
+        {view: 'checkbox', id: 'chk_config_add_same_product', labelWidth: 0,
+            labelRight: 'Permitir agregar el mismo producto'},
         ]},
     {maxHeight: 20},
     {template: 'Ayudas varias', type: 'section'},
diff --git a/source/static/js/ui/invoices.js b/source/static/js/ui/invoices.js
index 94252b1..80024cd 100644
--- a/source/static/js/ui/invoices.js
+++ b/source/static/js/ui/invoices.js
@@ -277,7 +277,7 @@ var grid_invoices = {
 
 
 var grid_details_cols = [
-    {id: "id", header:"ID", hidden: true},
+    {id: 'id_product', header: 'id_product', hidden: true},
     {id: 'delete', header: '', width: 30, css: 'delete'},
     {id: "clave", header:{text: 'Clave', css: 'center'}, width: 100,
         adjust: 'data'},
@@ -287,7 +287,8 @@ var grid_details_cols = [
     {id: "pedimento", header: 'Pedimento', editor: 'text', hidden: true},
     {id: "id_student", header: 'ID_Alumno', hidden: true},
     {id: 'student', header: 'Alumno', hidden: true, width: 150},
-    {id: "unidad", header:{text: 'Unidad', css: 'center'}, width: 100},
+    {id: "unidad", header:{text: 'Unidad', css: 'center'}, width: 100,
+        editor: 'select', options: 'values/unidades'},
     {id: 'cantidad', header: {text: 'Cantidad', css: 'center'}, width: 100,
         format: webix.i18n.numberFormat, css: 'right', editor: 'text'},
     {id: "valor_unitario", header:{text: 'Valor Unitario', css: 'center'},
diff --git a/source/templates/plantilla_factura.ods b/source/templates/plantilla_factura.ods
index b07c8b2..c2c7afe 100644
Binary files a/source/templates/plantilla_factura.ods and b/source/templates/plantilla_factura.ods differ