natural gas zemný plyn 3 [vynechat] heating 1 [vynechat] hydrates 1 [vynechat] hydráty 1 [vynechat] natural gas industry 1 [vynechat] ohrev vody 1 [vynechat] petroleum 1 [vynechat] petroleum processing 1 [vynechat] priemysel zemného plynu 1 [vynechat] ropa 1 [vynechat] spracovanie ropy 1 [vynechat] vykurovanie 1 [vynechat] water heating 1 [vynechat]