Referencing in the models

I have two schemas, a course and a section schema. I want to have a array of section title references from the section schema into the course schema instead of an array of section objectIds’ like that in the code. I have tried serveral options such a ‘ref’ and 'boundTo 'but none of these two methods worked. Note that the schemas are in two different file

// Mongoose model class for Courses
const mongoose = require("mongoose");
const { Schema } = mongoose;

// Class description
const courseSchema = new Schema({
  title: String,
  description: String,
  _user: { type: Schema.Types.ObjectId, ref: "User" },
  dateCreated: Date,
  dateUpdated: Date,
  coverImg: String,
  category: String,
  published: Boolean,
  sections: [{ type: Schema.Types.ObjectId, subRef: "Components" }],
});

const CourseModel = mongoose.model("courses", courseSchema); // Create new collection called courses, using the courseScema

module.exports = { CourseModel }

// Mongoose model class for Courses
const mongoose = require("mongoose");
const { Schema } = mongoose;

// Class description
const sectionSchema = new Schema({
  title: String,
  description: String,
  dateCreated: Date,
  dateUpdated: Date,
  components: [{ type: Schema.Types.ObjectId, ref: "Component" }],
});

const SectionModel = mongoose.model("sections", sectionSchema);

module.exports = { SectionModel }