Crypto Facilities and the CME Group  have been calculating and publishing the Bitcoin Reference Rate (BRR) since November 2016. Such an official rate is a prerequisite of options trading in the traditional markets. The BRR is calculated based on the rates from the biggest exchanges: Bitstamp, GDAX, itBit, and Kraken. More concretely, it is calculated based on all Bitcoin vs. USD trades on the participating exchanges between 3 and 4 p.m. London time. To calculate the BRR, the hour between 3 and 4 is divided into 12 intervals of 5 minutes. For each interval, the volume-weighted median of the Bitcoin price is calculated (statistically, the median, in contrast to the average, prevents single outliers from distorting the price). The BRR is then the average of these 12 median values. More details about the calculation of the BRR can be found in the BRR whitepaper.
The term altcoin has various similar definitions. Stephanie Yang of The Wall Street Journal defined altcoins as "alternative digital currencies,"[25] while Paul Vigna, also of The Wall Street Journal, described altcoins as alternative versions of bitcoin.[26] Aaron Hankins of the MarketWatch refers to any cryptocurrencies other than bitcoin as altcoins.[27]
The Funds may invest in foreign issuers, securities traded principally in securities markets outside the United States, U.S.-traded securities of foreign issuers and/or securities denominated in foreign currencies (together “foreign securities”). Also, each Fund may seek exposure to foreign securities by investing in Depositary Receipts (discussed below). Foreign securities may involve special risks due to foreign economic, political and legal developments, including unfavorable changes in currency exchange rates, exchange control regulation (including currency blockage), expropriation or nationalization of assets, confiscatory taxation, taxation of income earned in foreign nations, withholding of portions of interest and dividends in certain countries and the possible difficulty of obtaining and enforcing judgments against foreign entities. Default in foreign government securities, political or social instability or diplomatic developments could affect investments in securities of issuers in foreign nations. In addition, in many countries there is less publicly available information about issuers than is available in reports about issuers in the United States. Foreign companies are not generally subject to uniform accounting, auditing and financial reporting standards, and auditing practices and requirements may differ from those applicable to U.S. companies. Further, the growing interconnectivity of global economies and financial markets has increased the possibilities that conditions in any one country or region could have an adverse impact on issuers of securities in a different country or region.
Bitcoin has a very limited history of operations and there is no established performance record for the price of Bitcoin on the Bitcoin Exchange Market that can provide an adequate basis for evaluating an investment in bitcoin or Bitcoin Instruments such as Bitcoin Derivatives, ETNs and Bitcoin Securities. Although past performance is not necessarily indicative of future results, if bitcoin had an established history, such history might (or might not) provide investors with more information on which to evaluate an investment in the Funds.
•   Futures Position Limit Risk — Limits on the amount of futures any one entity can hold may negatively impact the Fund’s ability to meet its investment objective if such limits are reached and exceptions to such limits are not granted. Currently the position limits for bitcoin futures contracts are much lower than they are for most other futures contracts.
There's a lot of ins and outs which can get confusing in arbitrage trading. We won't go into the technicals of why futures contracts trade at a premium to spot price. You can read a full explanation here. If it's not of interest to you, all you need to know is that there's a tendency, the further out in time the futures contract expires, for the premium to spot to be higher and higher in nominal percentage terms.