I am looking for a book I read in junior high back in the early 80’s. I am guessing it was from the 1950s or 60s because the book was older looking with that canvas style cover and it was green. It was about 4ish siblings (some could have been friends) that went back in time or into another dimension to the prehistoric age. I think they went through some sort of shrubbery door, but not sure. I remember them, of course, trying to get back home, because there were dinosaurs and they didn’t have much food. They came across some sort of plant at some point that sustained them. I thought the title was something about being “Lost in Time”, “Forgotten World/Past”, etc. but just a guess. Thank you kindly for any help. I have Google searched and came across a couple of books about adults getting lost in prehistoric times but this was for sure about kids and I think they were siblings and maybe even a friend with them. Maybe the oldest being early teens down to a 7 year old. Again, thanks and I hope you can help!