The lead belongs to Suzann Pettersen and Mi Hyang Lee after first-round play in the Manulife LPGA Classic.
The two women each shot 64, turning in 8-under scorecards on the 72-par course.
This year's Classic is being held at the Whistle Bear Golf Club in Cambridge, Ontario, Canada.
Pettersen lost her notebook on the 6,613-yard Whistle Bear course recently, and had to write notes by hand this week.
She said the lack of a yardage book made her trust herself and her intuition during first-round play.
The strategy worked for her, resulting in six birdies in one sequence of eight holes.
"We woke up this morning to perfect conditions," said Norway's Pettersen.
"You can fire at pins and get to par fives, which is fun.I think it's the best way to set up a golf course and get low scores."
Crowding the leaders are Shanshan Feng, Gonzalez Escall, and Hyoo Joo Kim, each of whom shot 65 on the first round.
Emily Pedersen, Jodi Ewart Shadoff, and Alena Sharp shot 66 for the day.Caroline Masson, who won the tournament last year, scored 70.
Two dozen Tour rookies are competing in the LPGA Classic, the most at any tournament this year.
The Manulife LPGA Classic dates back to 2012.
First-year play was held at Grey Silo Golf Course in Waterloo, Ontario, Canada.
Manulife has announced that 2017 will be its last year as sponsor of the tournament.
The LPGA hopes to continue the event under new sponsorship, but nothing has been announced at this point.
The Classic concludes on Sunday, June 11.