Update keys.md

docs/intro/keys.md

@@ -39,7 +39,7 @@ Yes, but only in that keys can be _reset_ (ie. regenerated as a new key pair). I
 <blockquote class="info">
 <strong>Did you know?</strong><br /><br />
 
-As a brief word on the NEAR runtime, the subsystem that manages state transitions on the blockchain (ie. keeping things moving from one block to the next), it's worth understanding that the movement of the system happens in stages, called epochs, during which the group of validators does not change. The [Nightshade whitepaper](https://near.org/downloads/Nightshade.pdf) introduces epochs this way: "the maintenance of the network is done in epochs, where an epoch is a period of time on the order of days." and there's much more detail in the paper.
+As a brief word on the NEAR runtime, the subsystem that manages state transitions on the blockchain (ie. keeping things moving from one block to the next), it's worth understanding that the movement of the system happens in stages, called epochs, during which the group of validators does not change. The [Nightshade whitepaper](https://near.org/papers/nightshade) introduces epochs this way: "the maintenance of the network is done in epochs, where an epoch is a period of time on the order of days." and there's much more detail in the paper.
 
 At the beginning of each epoch, some computation produces a list of validators for the very next epoch (not the one that just started). The input to this computation includes all validators that have "raised their hand" to be a validator by staking some amount over the system's staking threshold. The output of this computation is a list of the validators for the very next epoch.
 
@@ -57,12 +57,12 @@ If validator keys are changed _during an epoch in which the validator is staking
 For concrete examples of keys being used as identifiers, you can see a list of validators and active nodes on various NEAR networks here:
 
 - NEAR testnet (staking currently disabled)
-  - https://rpc.testnet.near.org/status
-  - https://rpc.testnet.near.org/network_info
+  - `https://rpc.testnet.near.org/status`
+  - `https://rpc.testnet.near.org/network_info`
 
 - NEAR betanet
-  - https://rpc.betanet.near.org/status
-  - https://rpc.betanet.near.org/network_info
+  - `https://rpc.betanet.near.org/status`
+  - `https://rpc.betanet.near.org/network_info`
 
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