Egypt’s referendum on a controversial draft constitution has begun in embassies abroad, days before the vote is due to take place at home, BBC reports. But with many judges refusing to oversee the process, it is unclear whether the vote will take place on one day or continue the next week. The opposition has called for the entire referendum to be scrapped.The armed forces chief has announced plans for unity talks on Wednesday in an attempt to end the political crisis.The streets of Cairo were described as calm on Wednesday and army tanks remained deployed outside the presidential palace.Judges are required to supervise the referendum, but according to one of the main judges’ organisations as many as 90% of them are refusing to take part in the process. The main cities of Cairo and Alexandria, along with eight other governorates, would vote on 15 December, and a further 17 would vote the following weekend, a justice ministry source told the BBC.Voting has, however, begun in Egyptian embassies and consulates abroad, the official Mena news agency reports. An estimated 589,000 expatriates have until Saturday to cast their ballots, it says.