Using Chainlink's chosen set of nodes to pull price feeds. Deploy to remix with: https://remix.ethereum.org/#version=soljson-v0.6.2+commit.bacdbe57.js&optimize=false&gist=ab642dff256732c82594e7b124a0b3a5

getDataReferenceContract.sol

pragma solidity ^0.6.0;

import "https://github.com/smartcontractkit/chainlink/evm-contracts/src/v0.6/interfaces/AggregatorInterface.sol";

contract ReferenceConsumer {
  AggregatorInterface internal ref;
  
  /**
   * @dev Ropsten example _aggregator:
   * @dev   ETH/USD feed: 0x8468b2bDCE073A157E560AA4D9CcF6dB1DB98507
   * @dev More available from https://docs.chain.link/docs/reference-contracts
   */
  constructor(address _aggregator) public {
    ref = AggregatorInterface(_aggregator);
  }
  
  /**
   * @notice Returns the latest answer from the _aggregator
   * @dev The answer is multiplied by a constant, depending on the aggregator
   * @dev For example, the Ropsten ETH/USD feed is multiplied by 100,000,000
   * @dev See https://docs.chain.link/docs/using-chainlink-reference-contracts#use-the-reference-data
   */
  function getLatestAnswer() public view returns (int256) {
    return ref.latestAnswer();
  }
  
  /**
   * @notice Returns the latest update timestamp from the _aggregator
   */
  function getLatestTimestamp() public view returns (uint256) {
    return ref.latestTimestamp();
  }

  /**
   * @notice Returns historical data from previous update rounds
   */
  function getPreviousAnswer(uint256 _back) public view returns (int256) {
    uint256 latest = ref.latestRound();
    require(_back <= latest, "Not enough history");
    return ref.getAnswer(latest - _back);
  }

  /**
   * @notice Returns historical data from previous update rounds
   */
  function getPreviousTimestamp(uint256 _back) public view returns (uint256) {
    uint256 latest = ref.latestRound();
    require(_back <= latest, "Not enough history");
    return ref.getTimestamp(latest - _back);
  }
}