diff --git a/repository/Grafoscopio/GrafoscopioBrowser.class.st b/repository/Grafoscopio/GrafoscopioBrowser.class.st
index d30ce65..6b82125 100644
--- a/repository/Grafoscopio/GrafoscopioBrowser.class.st
+++ b/repository/Grafoscopio/GrafoscopioBrowser.class.st
@@ -368,7 +368,6 @@ GrafoscopioBrowser >> openFromFile: aFileName [
 	mainTree := GrafoscopioNode new
 		header: (currentChildren at: 1) parent header;
 		level: (currentChildren at: 1) parent level;
-		metadata: (currentChildren at: 1) parent metadata;
 	 	children: currentChildren.
 	browser openOn: mainTree children.
 ]
@@ -395,7 +394,6 @@ GrafoscopioBrowser >> openFromFileSelector [
 	mainTree := GrafoscopioNode new
 		header: (currentChildren at: 1) parent header;
 		level: (currentChildren at: 1) parent level;
-		metadata: (currentChildren at: 1) parent metadata;
 	 	children: currentChildren.
 	browser openOn: mainTree children.
 ]
diff --git a/repository/Grafoscopio/GrafoscopioDocumentation.class.st b/repository/Grafoscopio/GrafoscopioDocumentation.class.st
index 91cb8ca..41ac2b7 100644
--- a/repository/Grafoscopio/GrafoscopioDocumentation.class.st
+++ b/repository/Grafoscopio/GrafoscopioDocumentation.class.st
@@ -88,9 +88,11 @@ GrafoscopioDocumentation class >> listOutdated [
 ]
 
 { #category : #updating }
-GrafoscopioDocumentation class >> listOutdatedDocsIn: aDocumentsName [
+GrafoscopioDocumentation class >> listOutdatedDocsIn: aDocumentsListName [
 	"I return the list of all documentent where the local copy and the remote copy doesn't match"
-	^ (self perform: aDocumentsName asSymbol) documents reject: [ :doc | (self isFileUpdatedFor: doc) ]
+	aDocumentsListName ifNil: [ ^ self ].
+	aDocumentsListName ifEmpty: [ ^ self ].
+	^ (self perform: aDocumentsListName asSymbol) documents reject: [ :doc | (self isFileUpdatedFor: doc) ]
 ]
 
 { #category : #updating }
diff --git a/repository/Grafoscopio/GrafoscopioNode.class.st b/repository/Grafoscopio/GrafoscopioNode.class.st
index e371cea..5dc44fd 100644
--- a/repository/Grafoscopio/GrafoscopioNode.class.st
+++ b/repository/Grafoscopio/GrafoscopioNode.class.st
@@ -23,7 +23,6 @@ Class {
 		'node',
 		'level',
 		'nodesInPreorder',
-		'metadata',
 		'links',
 		'output'
 	],
@@ -176,13 +175,12 @@ GrafoscopioNode >> asMarkdown [
 	| markdownOutput |
 	
 	markdownOutput := '' writeStream.
-	self exportPreambleTo: markdownOutput.
+	self metadataAsYamlIn: markdownOutput.
 	(self preorderTraversal) do: [ :eachNode | 
 		(eachNode level > 0) 
 			ifTrue: [(eachNode hasAncestorTaggedAs: 'invisible') | (eachNode tags = 'invisible')
 							ifFalse: [ markdownOutput nextPutAll:  (eachNode markdownContent) ]]].
-	^markdownOutput contents 
-	
+	^markdownOutput contents
 ]
 
 { #category : #exporting }
@@ -262,9 +260,9 @@ GrafoscopioNode >> bodyAsCode [
 	| codeBody |
 	codeBody := '' writeStream.
 	codeBody 
-		nextPutAll:  ('~~~{.numberLines}'); lf;
+		nextPutAll:  '~~~{.numberLines}'; lf;
 		nextPutAll: (self body contents asString withInternetLineEndings); lf;
-	   nextPutAll:  ('~~~'); lf; lf.
+	   nextPutAll:  '~~~'; lf; lf.
 	^ codeBody contents
 ]
 
@@ -383,7 +381,7 @@ GrafoscopioNode >> exportCodeBlockTo: aStream [
 GrafoscopioNode >> exportCodeNodeTo: aStream [
 	"I convert the content of a node taged as 'código' (code) as pandoc markdown and put it 
 	into aStream."
-	(self headerStartsWith: '%output')
+	((self headerStartsWith: '%output') or: [ self headerStartsWith: '%metadata' ])
 		ifTrue: [ self exportCodeOutputTo: aStream ]
 		ifFalse: [ self exportCodeBlockTo: aStream ]
 ]
@@ -392,8 +390,9 @@ GrafoscopioNode >> exportCodeNodeTo: aStream [
 GrafoscopioNode >> exportCodeOutputTo: aStream [
 	"I convert the output of a node taged as 'código' (code) as pandoc markdown and put it 
 	into aStream."
+	(self headerStartsWith: '%metadata') ifTrue: [ ^ self ].
 	aStream nextPutAll:  ('~~~{.numberLines}'); lf.
-	aStream nextPutAll: ((Compiler evaluate: self body) asString withInternetLineEndings); lf.
+	aStream nextPutAll: (self output asString withInternetLineEndings); lf.
 	aStream nextPutAll:  ('~~~'); lf;lf.
 	^aStream contents 
 ]
@@ -551,9 +550,14 @@ GrafoscopioNode >> key: aUniqueKey [
 
 { #category : #accessing }
 GrafoscopioNode >> lastLink [
-	links ifNil: [ ^ '' ].
-	links ifEmpty: [ ^ '' ].
-	^ links last
+	self links ifNil: [ ^ '' ].
+	self links ifEmpty: [ ^ '' ].
+	^ self links last
+]
+
+{ #category : #accessing }
+GrafoscopioNode >> lastNetLink [
+	^ self links detect: [ :l | l asZnUrl isURL ]
 ]
 
 { #category : #accessing }
@@ -585,14 +589,24 @@ GrafoscopioNode >> links: anObject [
 { #category : #operation }
 GrafoscopioNode >> linksToMarkdownFile [
 	"I detect if the links contains any reference to a file ending in '.md' or '.markdown'"
-	self links ifNotNil: [ 
-		self links 
-			detect: [:l | (l endsWith: '.md') or: [ l endsWith: '.markdown']]
-			ifFound: [ ^ true ]
-			ifNone: [^ false]]
+	self links 
+		ifNotNil: [ 
+			self links 
+				detect: [:l | (l endsWith: '.md') or: [ l endsWith: '.markdown']]
+					ifFound: [ ^ true ]
+					ifNone: [^ false]].
+	^ false
 	
 ]
 
+{ #category : #operation }
+GrafoscopioNode >> localFilesLinks [
+	"I collect all the links that point to the local file system. Because is supposed that
+	links contains only references to remote URL or local files, anything that is not a URL is
+	treated as a loca file link."
+	^ self links reject: [ :l | l asZnUrl isURL ]	
+]
+
 { #category : #exporting }
 GrafoscopioNode >> margin [
 	"I define the same margin of the page used for PDF exportations"
@@ -635,14 +649,28 @@ GrafoscopioNode >> markdownContent [
 	^ markdownStream contents 
 ]
 
-{ #category : #accessing }
+{ #category : #operation }
 GrafoscopioNode >> metadata [
-	^ metadata
+	| mnode |
+	mnode := self root preorderTraversal detect: [:n | n headerStartsWith: '%metadata' ].
+	^ mnode output.
+	  
 ]
 
-{ #category : #accessing }
-GrafoscopioNode >> metadata: anObject [
-	metadata := anObject
+{ #category : #exporting }
+GrafoscopioNode >> metadataAsYamlIn: markdownStream [
+	"I convert the first '%metadata' node into a YAML preamble to be used by Pandoc exportation."
+	markdownStream
+		nextPutAll: '---';
+		lf.
+	self metadata
+		keysAndValuesDo: [ :k :v | 
+			markdownStream
+				nextPutAll: (k , ': ' , v asString) withInternetLineEndings;
+				nextPutAll: String cr ].
+	markdownStream
+		nextPutAll: '---';
+		lf; lf
 ]
 
 { #category : #movement }
@@ -683,7 +711,9 @@ GrafoscopioNode >> newNode [
 
 { #category : #accessing }
 GrafoscopioNode >> output [
-	^ output
+	self tags ~= 'código' ifTrue: [ ^ self ].
+	self body ifNil: [ ^ nil ].
+	^ (Compiler evaluate: self body) 
 ]
 
 { #category : #accessing }
@@ -691,6 +721,11 @@ GrafoscopioNode >> output: anObject [
 	output := anObject
 ]
 
+{ #category : #utility }
+GrafoscopioNode >> pandocOptions [
+	^ self metadata at: 'pandocOptions' ifAbsent: [ ^ '' ]
+]
+
 { #category : #accessing }
 GrafoscopioNode >> parent [
 	"Returns the parent of the current node"
@@ -715,20 +750,13 @@ GrafoscopioNode >> pasteFromClipboard [
 	
 ]
 
-{ #category : #exporting }
+{ #category : #operation }
 GrafoscopioNode >> preorderTraversal [
 	nodesInPreorder := OrderedCollection new.
 	self visitedGoTo: nodesInPreorder.
 	^ nodesInPreorder.
 ]
 
-{ #category : #accessing }
-GrafoscopioNode >> processOutput [
-	(self headerStartsWith: '%output')
-		ifFalse: [ ^ self ].
-	^ self output: (Compiler evaluate: self body)
-]
-
 { #category : #movement }
 GrafoscopioNode >> promote [
 	"Moves the current node up in the hierachy, making it a slibing of its current parent"
@@ -787,10 +815,10 @@ GrafoscopioNode >> removeNode: aNode [
 
 { #category : #accessing }
 GrafoscopioNode >> root [
-	"I return the node of the Grafoscopio tree that contains the receiver"
+	"I return the root node of the Grafoscopio tree, i.e the common ancestor of all other nodes"
 	self level = 0 
-		ifTrue: [ ^ self ]
-		ifFalse: [ ^ self ancestors first. ]
+		ifFalse: [ ^ self ancestors first ].
+	^ self
 ]
 
 { #category : #accessing }
@@ -838,8 +866,9 @@ GrafoscopioNode >> title [
 
 { #category : #operation }
 GrafoscopioNode >> visitLastLink [
-	links ifNil: [ self inform: 'This node has no associated links to visit'. ^ self ].
-	[WebBrowser openOn: self lastLink] fork.
+	self lastLink = '' 
+		ifTrue: [ self inform: 'This node has no associated links to visit'. ^ self ].
+	[WebBrowser openOn: self lastLink] fork
 ]
 
 { #category : #'add/remove nodes' }
diff --git a/repository/Grafoscopio/GrafoscopioNotebook.class.st b/repository/Grafoscopio/GrafoscopioNotebook.class.st
index ab572e3..43089b0 100644
--- a/repository/Grafoscopio/GrafoscopioNotebook.class.st
+++ b/repository/Grafoscopio/GrafoscopioNotebook.class.st
@@ -146,12 +146,16 @@ GrafoscopioNotebook >> exportAsPDF [
 	"I export the current tree/document to a PDF file, using pandoc and LaTeX external apps.
 	The latex engine used is xelatex, to minimize errors and warnings related with UTF8 support.
 	I suppose all them are already installed and defined in the system."
-	| pdfFile |
+	| pdfFile pandocCommand  |
 	self markdownFile exists ifFalse: [ self exportAsMarkdown ].
 	pdfFile := self markdownFile parent fullName,'/', self markdownFile basenameWithoutExtension, '.pdf'.
 	pdfFile asFileReference exists ifTrue: [ pdfFile asFileReference delete ].
-	OSProcess command: 'pandoc --latex-engine=xelatex ', self markdownFile fullName, ' -o ', pdfFile.
-	self inform: ('File exported as: ', String cr, pdfFile).
+	pandocCommand := 'pandoc ', 
+					self notebook pandocOptions, ' ',
+					self markdownFile fullName, ' -o ', pdfFile.
+	Transcript show: pandocCommand.
+	ExternalUnixOSProcess command: pandocCommand.
+	self inform: ('File exported as: ', String cr, pdfFile)
 ]
 
 { #category : #persistence }
diff --git a/repository/Grafoscopio/ManifestGrafoscopio.class.st b/repository/Grafoscopio/ManifestGrafoscopio.class.st
index f974317..dce7e08 100644
--- a/repository/Grafoscopio/ManifestGrafoscopio.class.st
+++ b/repository/Grafoscopio/ManifestGrafoscopio.class.st
@@ -22,6 +22,11 @@ ManifestGrafoscopio class >> ruleRBBooleanPrecedenceRuleV1FalsePositive [
 	^ #(#(#(#RGMethodDefinition #(#'GrafoscopioNode class' #cleanTreeRootReferences #true)) #'2017-03-27T22:18:17.447627-05:00') )
 ]
 
+{ #category : #'code-critics' }
+ManifestGrafoscopio class >> ruleRBCascadedNextPutAllsRuleV1FalsePositive [
+	^ #(#(#(#RGMethodDefinition #(#GrafoscopioNode #metadataAsYamlIn: #false)) #'2017-04-20T19:01:59.286212-05:00') )
+]
+
 { #category : #'code-critics' }
 ManifestGrafoscopio class >> ruleRBClassNameInSelectorRuleV1FalsePositive [
 	^ #(#(#(#RGMethodDefinition #(#'Documentation class' #current #true)) #'2016-10-07T19:39:23.013722-05:00') )