AutoCAD Visual LISP / AutoLISP :: SSGET For Selecting Multiple Objects

I have this code that I wrote years ago that I want to update to select two types of civil3d objects and show them selected with grips on the screen. This function works fine

(defun CELFEATURE ()
(ssget "_X" '((0 . "AECC_FEATURE_LINE")))
(setq sset (ssget "P"))
(if sset
(progn
(sssetfirst sset sset)
;(command "_.PROPERTIES")
)
)
)
(defun cF () (CELFEATURE))

but if I add the extra object like this which I assume is the wrong syntax i only get the second type of objects. Need correct syntax I should be using for selecting more than one object in an ssget statement.

(defun CELFEATURE ()
(ssget "_X" '((0 . "AECC_FEATURE_LINE","AECC_AUTO_CORRIDOR_FEATURE_LINE")))
(setq sset (ssget "P"))
(if sset
(progn
(sssetfirst sset sset)
;(command "_.PROPERTIES")
)
)
)

(defun cF () (CELFEATURE))