Thanks for creating the tutorial using OpenZeppelin Contracts.

Can you please specify the release version on the imports, otherwise you import the master branch.

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.3.0/contracts/token/ERC721/ERC721Full.sol";
// Importing OpenZeppelin's SafeMath Implementation
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.3.0/contracts/math/SafeMath.sol";

https://github.com/openberry-ac/cryptovipers/issues/2

Software Engineer (blockchain)

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