diff --git a/polkadot/cli/src/lib.rs b/polkadot/cli/src/lib.rs
index c1cd29dfce..7de2ed9d5d 100644
--- a/polkadot/cli/src/lib.rs
+++ b/polkadot/cli/src/lib.rs
@@ -64,7 +64,7 @@ pub trait Worker: IntoExit {
 
 	/// Return configuration for the polkadot node.
 	// TODO: make this the full configuration, so embedded nodes don't need
-	// string CLI args
+	// string CLI args (https://github.com/paritytech/polkadot/issues/111)
 	fn configuration(&self) -> service::CustomConfiguration { Default::default() }
 
 	/// Do work and schedule exit.
diff --git a/polkadot/network/src/collator_pool.rs b/polkadot/network/src/collator_pool.rs
index a903470bc6..bfec39736f 100644
--- a/polkadot/network/src/collator_pool.rs
+++ b/polkadot/network/src/collator_pool.rs
@@ -184,7 +184,7 @@ impl CollatorPool {
 		if let Some(para_id) = self.collators.get(&collator_id) {
 			debug_assert_eq!(para_id, &collation.receipt.parachain_index);
 
-			// TODO: punish if not primary?
+			// TODO: punish if not primary? (https://github.com/paritytech/polkadot/issues/213)
 
 			self.collations.entry((relay_parent, para_id.clone()))
 				.or_insert_with(CollationSlot::blank_now)
@@ -205,6 +205,7 @@ impl CollatorPool {
 	/// Returns a set of actions to perform on the network level.
 	pub fn maintain_peers(&mut self) -> Vec<Action> {
 		// TODO: rearrange periodically to new primary, evaluate based on latency etc.
+		// https://github.com/paritytech/polkadot/issues/214
 		Vec::new()
 	}
 
diff --git a/polkadot/network/src/lib.rs b/polkadot/network/src/lib.rs
index 8c80114bca..b979481dc8 100644
--- a/polkadot/network/src/lib.rs
+++ b/polkadot/network/src/lib.rs
@@ -145,6 +145,7 @@ impl PeerInfo {
 pub enum Message {
 	/// As a validator, tell the peer your current session key.
 	// TODO: do this with a cryptographic proof of some kind
+	// https://github.com/paritytech/polkadot/issues/47
 	SessionKey(SessionKey),
 	/// Requesting parachain block data by (relay_parent, candidate_hash).
 	RequestBlockData(RequestId, Hash, Hash),
diff --git a/polkadot/network/src/tests/validation.rs b/polkadot/network/src/tests/validation.rs
index a61fa5a80d..d9cf88b622 100644
--- a/polkadot/network/src/tests/validation.rs
+++ b/polkadot/network/src/tests/validation.rs
@@ -148,6 +148,7 @@ impl NetworkService for TestNetwork {
 		let mut context = TestContext::default();
 		let res = with(&mut *self.proto.lock(), &mut context);
 		// TODO: send context to worker for message routing.
+		// https://github.com/paritytech/polkadot/issues/215
 		res
 	}
 }
diff --git a/polkadot/parachain/src/lib.rs b/polkadot/parachain/src/lib.rs
index fe2c388ca9..7ae5399597 100644
--- a/polkadot/parachain/src/lib.rs
+++ b/polkadot/parachain/src/lib.rs
@@ -79,7 +79,7 @@ pub mod wasm_executor;
 pub mod wasm_api;
 
 /// Validation parameters for evaluating the parachain validity function.
-// TODO: balance downloads
+// TODO: balance downloads (https://github.com/paritytech/polkadot/issues/220)
 #[derive(PartialEq, Eq, Decode)]
 #[cfg_attr(feature = "std", derive(Debug, Encode))]
 pub struct ValidationParams {
@@ -92,7 +92,7 @@ pub struct ValidationParams {
 }
 
 /// The result of parachain validation.
-// TODO: egress and balance uploads
+// TODO: egress and balance uploads (https://github.com/paritytech/polkadot/issues/220)
 #[derive(PartialEq, Eq, Encode)]
 #[cfg_attr(feature = "std", derive(Debug, Decode))]
 pub struct ValidationResult {
diff --git a/polkadot/primitives/src/lib.rs b/polkadot/primitives/src/lib.rs
index 96125c4d63..de3bbdad26 100644
--- a/polkadot/primitives/src/lib.rs
+++ b/polkadot/primitives/src/lib.rs
@@ -59,7 +59,7 @@ use primitives::bytes;
 
 /// An index to a block.
 /// 32-bits will allow for 136 years of blocks assuming 1 block per second.
-/// TODO: switch to u32
+/// TODO: switch to u32 (https://github.com/paritytech/polkadot/issues/221)
 pub type BlockNumber = u64;
 
 /// Alias to 512-bit hash when used in the context of a signature on the relay chain.
diff --git a/polkadot/primitives/src/parachain.rs b/polkadot/primitives/src/parachain.rs
index 8a88c5de0e..563d6f4ab4 100644
--- a/polkadot/primitives/src/parachain.rs
+++ b/polkadot/primitives/src/parachain.rs
@@ -152,6 +152,7 @@ impl PartialOrd for CandidateReceipt {
 impl Ord for CandidateReceipt {
 	fn cmp(&self, other: &Self) -> Ordering {
 		// TODO: compare signatures or something more sane
+		// https://github.com/paritytech/polkadot/issues/222
 		self.parachain_index.cmp(&other.parachain_index)
 			.then_with(|| self.head_data.cmp(&other.head_data))
 	}
diff --git a/polkadot/runtime/src/parachains.rs b/polkadot/runtime/src/parachains.rs
index 6fbb90a88b..21d707c067 100644
--- a/polkadot/runtime/src/parachains.rs
+++ b/polkadot/runtime/src/parachains.rs
@@ -425,7 +425,7 @@ impl<T: Trait> Module<T> {
 	}
 
 /*
-	// TODO: Consider integrating if needed.
+	// TODO: Consider integrating if needed. (https://github.com/paritytech/polkadot/issues/223)
 	/// Extract the parachain heads from the block.
 	pub fn parachain_heads(&self) -> &[CandidateReceipt] {
 		let x = self.inner.extrinsics.get(PARACHAINS_SET_POSITION as usize).and_then(|xt| match xt.function {
diff --git a/polkadot/validation/src/collation.rs b/polkadot/validation/src/collation.rs
index d9a84c0f46..f260274f50 100644
--- a/polkadot/validation/src/collation.rs
+++ b/polkadot/validation/src/collation.rs
@@ -48,7 +48,7 @@ pub trait Collators: Clone {
 	/// will be passed to the `TableRouter` instance.
 	fn collate(&self, parachain: ParaId, relay_parent: Hash) -> Self::Collation;
 
-	/// Note a bad collator. TODO: take proof
+	/// Note a bad collator. TODO: take proof (https://github.com/paritytech/polkadot/issues/217)
 	fn note_bad_collator(&self, collator: CollatorId);
 }
 
diff --git a/polkadot/validation/src/lib.rs b/polkadot/validation/src/lib.rs
index 739bf5aacf..0597f8cfe2 100644
--- a/polkadot/validation/src/lib.rs
+++ b/polkadot/validation/src/lib.rs
@@ -797,7 +797,7 @@ impl<C, TxApi> CreateProposal<C, TxApi> where
 				.join(", ")
 		);
 
-		// TODO: full re-evaluation
+		// TODO: full re-evaluation (https://github.com/paritytech/polkadot/issues/216)
 		let active_parachains = runtime_api.active_parachains(&self.parent_id)?;
 		assert!(evaluation::evaluate_initial(
 			&new_block,
diff --git a/polkadot/validation/src/shared_table/mod.rs b/polkadot/validation/src/shared_table/mod.rs
index cea2f1ef92..92e420d355 100644
--- a/polkadot/validation/src/shared_table/mod.rs
+++ b/polkadot/validation/src/shared_table/mod.rs
@@ -139,6 +139,7 @@ impl SharedTableInner {
 		let digest = &summary.candidate;
 
 		// TODO: consider a strategy based on the number of candidate votes as well.
+		// https://github.com/paritytech/polkadot/issues/218
 		let do_validation = para_member && match self.validated.entry(digest.clone()) {
 			Entry::Occupied(_) => false,
 			Entry::Vacant(entry) => {