getSlideByIndices( h, v ) {

		const page = this.getAllPages().find( page => {
			return page.indexh === h && page.indexv === v;
		} );

		return page ? page.slideElement : null;

	}
Retrieve a slide by its original h/v index (i.e. the indices the
slide had before being linearized).

@param {number} h
@param {number} v
@returns {HTMLElement}