South America - Proof of onward travel if arriving in Bolivia by air

I just read on the Government of Canada's travel report for Bolivia that "On August 29, 2007 the Bolivian government introduced a new regulation which requires that all visitors arriving by air be able to produce a return air ticket or another proof of how they plan to leave the country at the end of their stay."

I'll be arriving in La Paz by air but will be exiting by bus to Peru via Lake Titicaca. I won't have a bus ticket or anything before arriving in Bolivia. Does anyone know what kind of proof I should supply upon arrival to show that I'll be leaving the country? I should clarify that I have a return ticket from Buenos Aires back to Toronto for 6 weeks after I enter Bolivia, as well as tickets for flights throughout Peru, from Peru to Chile, from Chile to Argentina and throughout Argentina.

I take you'll carry the printout of your flight itineraries with you. Showing that you have all these other flights scheduled and, most important, the EZE-YYZ flight coming up will demonstrate that you are leaving Bolivia.

SJOGuy: Thanks. That's what seems logical and rational to me too, but I read a few stories online about people who had problems with this rule despite having flights out of other parts of SA, which makes me feel a bit anxious about it. Just wondering if anyone here has had any experiences with this issue?