Well it's the strongest, anyway. It is hard for someone who doesn't have the skin disease vitiligo to get a dermatologist or even their GP to prescribe it for them. I once just told a GP that it was just monobenzyl ether of hydroquinone and she went ahead and prescribed it at the 40% I asked for. If you happen to get a doctor who studied medicine in another country it gets easier. This one was from Switzerland...GP's tend not to know what it is exactly, and doctors from other countries aren't as paranoid about it.
That being said, it's easier if you just order the raw material from overseas from places like China or the Philippines where they manufacture it for the drug industry. Some of them don't care who they send it to as long as they receive payment! They'll ship it discreetly but it will take a little while to arrive.
Desperate times call for desperate measures.