Merge pull request #1246 from iotaledger/addManaArticle

Add mana article

docs/learn/protocols/iota2.0/core-concepts/data-flow.md

@@ -27,7 +27,7 @@ Since nodes have finite capabilities, the network can process a limited number o
 
 The application layer lives on top of the communication layer. The application layer is mainly related to objects called payloads (e.g., transactions are a type of payload). Anybody can develop applications on this layer, and nodes can choose which applications to run. Of course, these applications can also be dependent on each other.
 
-Nodes must also run several core applications, such as the engine, which maintains the [ledger state](data-structures.md) and a quantity called Mana. Mana is a scarce resource that serves as a Sybil protection mechanism and spam protection. All nodes must also run the Approval Weight and Finality Gadget application, which provides a protocol that produces consensus between nodes on whether blocks are to be included in the Tangle (instead of being orphaned) and on whether transactions inside included blocks should mutate the ledger (instead of being deemed non-mutating). Lastly, the same gadget enables nodes to reorganize their perception of the Tangle when necessary, using the fork-choice rule.
+Nodes must also run several core applications, such as the engine, which maintains the [ledger state](data-structures.md) and a quantity called [Mana](mana.md). Mana is a scarce resource that serves as a Sybil protection mechanism and spam protection. All nodes must also run the Approval Weight and Finality Gadget application, which provides a protocol that produces consensus between nodes on whether blocks are to be included in the Tangle (instead of being orphaned) and on whether transactions inside included blocks should mutate the ledger (instead of being deemed non-mutating). Lastly, the same gadget enables nodes to reorganize their perception of the Tangle when necessary, using the fork-choice rule.
 
 ## 4. Data Flow
 
@@ -177,7 +177,7 @@ The tip selection mechanism performs a uniform random tip selection from a subse
 
 After selecting parents, the algorithm chooses the type of reference (strong, weak, etc.) it uses for each parent, depending on the opinion the node has about the past cones of these parents.
 
-Finally, if the block being issued is a validation block, the tip selection may differ from the tip selection of regular blocks; specifically, committee members will always try to reference all known blocks from other committee members (in addition to the random tips).
+Finally, if the block being issued is a [validation block](mana.md#validation-blocks), the tip selection may differ from the tip selection of regular blocks; specifically, committee members will always try to reference all known blocks from other committee members (in addition to the random tips).
 
 ### 4.7 Consensus and Notarization