All examples are mine.
Could you help me to deal with them?
(1a) There are some thousand people. - as far as I know, it's correct
(1b) There are some a thousand people. - ??? (I don't know if it's correct)
(1c) There are some one thousand people. - as far as I know, it's correct
(2a) There are about thousand people. - ??? (I don't know if it's correct)
(2b) There are about a thousand people. - I'm sure it's correct
(2c) There are about one thousand people. - I'm sure it's correct